But, at the same time: Cloudflare isn't going to serve me a cache from Seattle, Manchester, or Tokyo. Pinning down an unknown Signal user to even a rough geographic location is an important bit of metadata that could combine to unmask an individual. Neat attack!
If you're allowing user uploaded content, and you use Cloudflare as a CDN, you could mitigate and provide your users with plausible deniability by prefetching each uploaded URL from random data centers. But, of course, that's going to make your Cloudflare bill that much more expensive.
Cloudflare could allow security-sensitive clients to hide the cache-hit header and add randomized latency upon a cache hit, but the latter protection would also be expensive in how many connections must be kept alive longer than they otherwise would. Don't do anything on a personal device or account if you want your datacenter to be hidden!
(EDIT: Apparently signal e2e encrypts images prior to upload, so pre-fetching the encrypted blob from one or multiple servers would in fact be a mitigation of this attack.)
I do wonder if Telegram is as invulnerable as the author assumes. They might not be using Cloudflare for caching, or even HTTP, but the basic elements of this attack might still work. You’d just need to modify the “teleport” aspect of it.
The DC that a user is associated with is exposed by the API - you don't need to get them to upload a file to discover it - but it's so broad that it's not much of a deanonymizing signal. (Knowing that your target is in DC1, for example, just means that they're probably somewhere in North or South America. Or that they registered using a phone number that said they were.)
Add unique urls.
Maybe just avoid it altogether.
The problem in this case isn't cloudflare. The problem is that these images load without the user's interaction and the person sending it gets to choose if it's cloudflare or not. So your statement within this context doesn't really work.
I dunno, I'd still say the problem is at least 50% cloudflare. Why should they make which datacenters have a resource cached be obvious public knowledge? I do agree though, one could still end up inferring this information noisily by sending an attachment, waiting a while, and then somehow querying a lot of DCs and trying to infer times to see if it's cached or not.
Personally, I've never been a fan about so many things like URLs being so public. I get the benefits of things like CDNs and what not and the odds of guessing a snowflake value and what not, but still...all attachments in Discord are public. If you have a URL, you have the attachment. And they're not the only ones with this kind of access model.
Personally, like you I’m also not a huge fan of this, but URLs like that basically should be treated as the passwords. Don’t post them publicly / don’t give them out to people you don’t trust.
I use it to share memes and shitpost but definitely not something to share sensitive content IMO.
Edit: Actually... (in signal's case) it might be possible to provide the user's device 2 tokens, 1 to access the url and 1 to issue new access links. Then the user can request a new access link with their second token when their url access token expires. Signatures would help prevent it from needing to be stored in the database. It would be interesting to try.
Edit2: Also I am now curious... does this mean only text messages are e2ee? yikes.
The problem here is avatar URLs.
[0] https://www.bleepingcomputer.com/news/security/discord-will-...
But agree with your statement here and others about the lifetime of the data - if something is sensitive or secret you want proper access controls applied, not just openssl rand -hex 8
I agree that having it in the header for everyone is maybe too obvious. But you could otherwise infer that from timing.
Your defense doesn't really work. Sure many entities could share blame but the one fix is getting rid of cloudflare.
I have this old site to test this (the list of sites is a bit old): https://cloudflare-test.judge.sh/
If it was any less specific we'd be talking about a deanonymization attack that outs whether or not a target is still on Earth.
Looking at the app options it seems to be possible to disable media auto-download entirely; there's tickboxes for Images/Audio/Video/Documents via Mobile Data/Wi-Fi/Roaming.
Do you think a large proportion of Signal users also use VPNs? I'd expect it would be a higher proportion than the general population but still only a small minority.
It is feasible to consider that interesting Signal users mostly use VPN as an extra protection layer.
If you fear for your life you are much more likely to have spent time researching how to protect yourself digitally.
That's a HN reader. For the non-technical, it is a minefield.
Although. it has edge usecases even for "normal people":
Eg. you suspect your coworker to be catfishing you on eg. discord, you know that he's in your city now, verify, then wait for him to leave for a vacation to somewhere abroad, check again.
So though this does have implications, the assumptions they utilise, like always, are not universal.
CLoudflare uses anycast, and IP geo location is not how anycast works.
The L2 FTTN parts of the NBN have been known to have an RTT in the range of minutes, for some locations.
My own varies from 5ms, for those who don't assume my geography, out to 890ms for those that do.
CloudFlare get to see a fuckton of metadata from private and group chats, enough to trace who originally sends a piece of media (identifiable from its file size), who reads it, when it is is read, who forwards it and to whom. It really doesn't matter that they can't see an image or video, knowing its size upfront or later (for example in response to a law enforcement request) is enough
This is an overly binary take. Security is all about threat models, and for most of us the threat model that Signal is solving is "mainstream for-profit apps snoop on the contents of my messages and use them to build an advertising profile". Most of us using it are not using Signal to skirt law enforcement, so our threat model does not include court orders and warrants.
Signal can and should append some noise to the images when encrypted (or better yet, pad them to a set file size as suggested by paulryanrogers in a sibling comment) to mitigate the risks of this attack for those who do have threat models that require it, but for the vast majority of us Signal is just as fit for purpose as we thought it was.
People who are doing work to help people in ways the state tries to prevent (like giving people food) rely on this tech. These are the same groups who were able to mobilize so quickly to respond to the LA fires, but the Red Cross & police worked to shut down.
This impacts the people who are there for you when the state refuses to show up. This impacts the future version of you who needs it.
Most people aren't disabled, yet. Doesn't mean they don't need us building infrastructure for if/when they become disabled.
The powerful entities tend to prohibit relief to the oppressed side, even making it illegal.
But, truly, I think you’re right to highlight wars.
https://www.salon.com/2023/08/07/criminalizing-the-samaritan...
Not sure that encrypted email in general would be less secure than, say, Signal. Since Signal is an instant messenger on a phone it might actually be less secure[1].
Also Marlinspike and Whittaker are quite outspoken about mass surveillance.
If cloudflare can compile a big part of the "who chats with whom" graph, that is a system design defect.
It was not clear to most people that their highly sensitive info was being uploaded to the cloud at all let alone that it was only protected by the PIN. I wouldn't be surprised if a lot of people picked something as simple as possible.
https://old.reddit.com/r/signal/comments/gqc2hu/the_new_pin_...
Far from ideal I agree.
Adding padding to the image wouldn't do anything to stop this "attack". This is just watching which CF datacenters cache the attachment after it gets sent.
> It really doesn't matter that they can't see an image or video, knowing its size upfront or later (for example in response to a law enforcement request) is enough
Doesn't this open up the possibility to identify groups that have been infiltrated by spies or similar posers? If you use this method to kinda-sorta locate or identify all the users in your group and one or more of those users ends up being located in a region where you should have no active group members then you may have identified a mole in your network.
Just thinking out loud here since there's no one else home.
...unless they happen to be using a VPN for geo-unblocking reasons or whatever.
The only reason we assume they don't do this is because it's a waste of resources for no good reason. But what if somebody gave them a good reason?
Ideally, the image should be padded, encrypted with a different key, and given a different URL for each user who is authorized to view it. But this would increase the client's burden significantly, especially in conversations that include more than two people.
You misspelled "I do not understand what end to end encryption means"
Say for example that you're an investigating agent in regular contact with someone.
A single data-point wouldn't mean anything. However, a sequence of daily image retrievals might tell you that they spend 90% of their time in WA and 10% of their time elsewhere.
That information alone still might not mean anything, but if you also have a specific suspect in mind, it may help confirm it. Or if you have access to the suspected person directly, if you're able to also befriend their "clean" profile, you might be able to pull the same trick and correlate the two location profiles.
De-anonymisation isn't about single pieces of information, but all information helps feed into a profile to narrow suspects or confirm suspicions.
( By "agent" I just mean a person, not an AI agent nor Law enforcement, who could presumably just get the information more directly from cloudflare. )
Not really. Any public meme group is inevitably going to be monitored by intelligence agencies, and you should assume as such. Even if it isn't, I can imagine agitators from the other side joining the group with a Russian VPN to poison the well. If there's a private group of people that you supposedly trust, any competent mole is going to be using device/network level VPN to cover their tracks. Otherwise they're 1 click away (eg. if someone shared a link) from an opsec fail.
And to someone else's point - they had to block the request on their end with a MITM to do the 1-click version on signal. No such MITM is needed with the friend request.
As an aside, one time i got doxxed hard in an IRC channel with several hundred active users. I had a suspicion of who it was, and i knew they lived in chicago. So i "accidentally" sent a link to "screenshot proof" that was hosted on one of my domains. there was 1 immediate click. instant. Chicago. "accidentally" because it looked like i pasted an email body.
Packed the real screenshot and a complaint to the ircadmin. they said "and so you dox them back?"
can't win for trying.
Whether this specific level/type of deanonymization is a problem for your particular use case is an entirely different question. Personally, I wouldn't even care if mutual contacts were to see my IP address outright (and they do for calls), but I'm not every user.
But my PBX and my matrix server both use coturn. Our 10 user "private" PBX we have to VPN into a fortigate in a DC to use, but to my understanding, there's literally no way to eavesdrop on those calls without already compromising the server it's running on, and if that's the case, no extra VPN steps or whatever will help.
anyhow even with a real, publicly routable IP, stock windows 11, stock macos (used to be true), and most linuxes won't get compromised by stuff like backorifice or whatever else l0pht put out as "remote administration tools". that is, there usually isn't any listening ports on a public IP these days. Shield's Up!
That's probably correct (with the caveat that I suspect NSA/FSB/MSS/Mossad/whoever can reasonably be assumed to have backdoored Fortinet)
There is still the problem that an attacker with "global passive observer" capabilities (which almost certainly includes most non 3rd world nation states, and probably a few of the more problematic 3rd world ones too) can still do traffic analysis to uncover your social network (or criminal/terrorist/whistleblower/journalistic network) by identifying the call traffic endpoints.
Considering the almost weekly discovery of fortinet vulnerabilities that seems like a rather low bar
I suspect you're looking at that wrong.
It's each internet connection that gets a /64, not each machine. Your ISP hands you a /64 and you can do whatever you like with it on your home(/corporate) network.
So you can choose from 18 thousand trillion IPV6 addresses for any machine behind your ISP/internet connection, but the top half of your IPV6 address uniquely identifies that ISP and they can connect that to your account/payment details, with 4 billion times as much precision as an IPV4 address.
i get a /48, which i can delegate the prefix to 255 subnets of size /64, so each machine on my LAN gets a /64 this is Prefix Delegation, part of DHCP v6 aka DHCP-PD
edit: this is still "new" in that half the consumer routers only partially support it. but afaik it was in the spec for ipv6 that each node should be a /64, so realistically my LAN having each node with /64 is per spec, and machines that are NAT behind a single /64 at the gateway are out of spec and part of the reason that no one uses ipv6, IMO...
If i visit some site via v6 on my desktop today and in a month from my phone, at home via v6 over wifi, what percentage of companies will pool those two devices (assuming no pooling from merely being my device, etc). Either ipv6 is a nightmare or it's the utopia we were promised i will accept no compromises.
There was a real example of that amount of information being relevant in the Silk Road investigation. Ulbricht accidentally revealed his timezone early on, which was useful to US authorities since it narrowed him down to being in the US, whereas without that information he could have been from anywhere in the world.
Anyone who wants to conceal what continent they're on will also be using a VPN 24/7, or will have the proxy setup in Signal (AKA running 24/7), which defeats this.
This is a neat demo, but it should not fundamentally alter the way that anyone is using Signal. Either it doesn't matter to you or you already have mitigations in place.
The problem is, nobody's threat model includes state level attackers, until one day it does.
Back when Ulbricht was publicly asking questions using an easily uncovered identity, he wasn't thinking that in a few years he'd have the full force of every relevant TLA in the US (and Five Eyes/14 Eyes) trying to track him down.
Yes, it's vogue right now to speculate that what you're doing right now could suddenly become illegal in a new administration, but if that happens tomorrow, most of us would be one of hundreds of thousands who are all in the same boat. For that reason, most of us won't get targeted retroactively for behaviors that were legal at the time, and we have the option to reevaluate our security posture when the political landscape changes.
But yeah, if you're actively speculating about starting an illegal service today, you should definitely have a better security posture than Ulbricht did.
I'm probably more paranoid than needed, but I'm way less sure than you seem to be about being able to hide as one of a few hundred thousand needles in the US public haystack.
I, for one, would be terrified right now if I were the child of illegal immigrants. The hateful portion of the hard right are gleefully looking forward to ICE rounding up hundreds of thousands of people.
You should probably be concerned if you were publicly pro-choice a few years back. Or if you came out as trans. Or got gay married. Or any of probably hundreds of other things that most people would have thought perfectly safe and socially reasonable in the recent past, which are looking much less so today.
I'm sure that would be part of any oppressive government's plan. They wouldn't go after people for their past "transgressions" as long as they keep their heads down, do as they're told, and don't cause any trouble. At that point you're morally compromised.
We used everything, from browser fingerprinting (and EFF only made the world aware of it 6 years later), looking them up in databases, tracing every digital evidence they left, etc.
Every little thing counted. What I learned is that people leave a lot of traces and you can collect these traces to dox them. The way you write is even sometimes fairly identifiable.
Or send this to a bunch of signal users whom you suspect one of them being a particular person, and if you know that the person you are looking for is going to travel you can send it once before and once after. Then see which of these users were in the home city and subsequently in the destination city.
There really should be a "never use the internet without VPN" mode on devices.
So if there's no always-on hardware maintaining that VPN connection, probably the phone is going to wake up without it. And even if it auto-reconnects, it'll probably load stuff before it's connected to the VPN.
Does the caching occur even if both users are online when the attachment is sent?
Locating the superlab to within 800 miles would break Gus' threat model.
Combined with the information the police have, which is that a new form of "blue meth" is spreading across the American southwest, a reasonable conclusion would be that the "underground superlab" is where the meth is being manufactured. It's independent corrobation of a major manufacturing operation occurring in the United States in the exact region where a new drug is taking off.
This is useful, since it helps rule out the meth being smuggled in from Mexico. It also makes the lab a high priority target, because a DEA agent investigating doesn't need to liaise with a foreign government, and you can secure a domestic prosecution + American prison time instead of attempting to extradite the cooks.
It also allows me to send a detailed memo about the superlab to ASAC Schrader's office in Albuquerque telling him about a threat in his jurisdiction, rather than circulating a brief summary about this superlab in the weekly intelligence briefing sent to all high-ranking DEA officials they probably don't read.
You can plot the timestamps of every message, read receipt and emoji reaction, which gives you the timezone and hints at work schedule, commute duration and vacations.
Often people will post photos or have profile pictures.
Say you have a photo taken at a random mcdonalds. That'd be 36'000 locations. Imagine cloudflare location and timezone help you narrow it down to new mexico. That's 80 locations. Small enough that you can look at every single one using street view and check where the photo actually was taken.
Now you can subpoena the McDonald's cctv footage and figure out who sent that picture.
If you can see outside of the McDonalds for street view to be usable, you're almost certainly able to determine what country it is in, and potentially the exact location, depending on what is visible outside.
If it's a picture that shows the menu, well, street view isn't likely to be super useful, but you'd have a trivial time figuring out what country it is in at that point - menus vary from country to country, even when they are still in English.
New Mexico has relatively few McDonald's restaurants because New Mexico has a fairly low population - only 2.1m for the whole state. With that in mind, it seems unlikely that that Cloudflare has a close enough POP for you to be able to specifically decide it's NM.
If I can see enough for Street View to be able to confirm location, it seems like I can just search via the data there and get far more narrowed down results. If I can see a Burger King and a Best Buy outside from the picture, I can just use one of the many mapping services with APIs to get a list of all McDonalds locations within a tenth of a mile of a Burger King and Best Buy and look through a smaller list. If I'm confident of the time zone, like you suggest we should be able to be, then that's an even smaller list.
I'm not saying this attack is useless by any means, but I don't see a world where the sharing of the pictures to begin with isn't the most significant opsec failure and doesn't open you up to being de-anonymized in a myriad of other ways.
>Say you have a photo taken at a random mcdonalds. That'd be 36'000 locations. Imagine cloudflare location and timezone help you narrow it down to new mexico. That's 80 locations. Small enough that you can look at every single one using street view and check where the photo actually was taken.
Sounds like the bigger opsec failure is posting the pictures, and the leaking the cloudflare POP only makes the search slightly easier.
I would not define 3 orders of magnitude as "slightly easier".
(But notifications are already a bad idea for opsec anyway.)
That's why the attack is contrived. If you have poor opsec you don't need need this attack at all. You can probably get the victim's exact IP by getting him to click on a link, or sending him an email. If he has good opsec he's going to be using a VPN that renders this attack useless. For this attack to be valuable you need a guy who has such good opsec that you can't get his location any other way, but for whatever reason isn't using an always-online VPN.
For example, imagine someone suspected of sharing sensitive information with a journalist. They might have a short list of suspects, and use this technique to confirm which one it is. They might identify which journalist it is - maybe only a limited number cover this beat.
This is very very bad.
Not necessarily. Cloudflare is very upfront that they do not cache everything, and the time things are cached can vary greatly.
The kid keeps talking about "deanonymization" and he has no idea what the term actually means.
Agree, good writeup, but also a stretch to say they are "pinpointing" anyone's location.
Surprised signal doesn't have this option.
I only message people I know on Signal anyway.
Edit: it seems signal does have the option
Signal could mitigate this with something similar, where it didn't load the image file AT ALL, and instead showed a message:
<User> wants you to load an image from https://example.com/foo.png. Load image? > Yes > No
The only case where it might be downloaded more than once is if the user has multiple clients. Not that common and still very little traffic.
There's definitely cases where this is going to be immediately used. Shit, just using it to scrape Cloudflare for additional metadata on everyone from other user table leaks is probably valuable data. Even triangulation over time as they move around is going to get a more precise result. Maybe you find a vulnerability that takes that cloudflare node offline and run it again, repeat until you've got a fairly small radius they could be in.
Yeah and in that case there won't be a data center because who puts one in places without clients nearby? :)
I'll echo the other comments and say "deanonymization" is stretching the definition of the word, along with "grab the user's location", as it isn't anything near precise. 150 miles is approx. a 2-hour drive on the highway from Atlanta, GA to Augusta, GA. In that radius, there's probably 700,000+ people.
I do think the auto-retrieve attachment feature of Signal is slightly concerning, as for a private messenger I'd expect there to be an option to turn it off (like turning off JS in Tor). I don't know if I'm not looking deep enough, but there doesn't seem to be a feature for that.
Signal appears to take a useful-by-default approach that balances privacy and ease-of-use in order to encourage adoption by the masses, I'd assume most people that are really concerned are hardening Signal, similar to what is in this guide: https://www.privacyguides.org/articles/2022/07/07/signal-con... . They've always recommended a VPN / proxy + a modification of settings for more high-security scenarios.
Caching isn't going anywhere, and neither is CloudFlare. The DoSing days of old in P2P multiplayer lobbies with exposed IPs seemed to carry more of a threat than this, CloudFlare's response seems to be the best out of the 3. Caching sensitive information is never recommended and the onus is on the application doing the communicating to tell their CDN / middle-service to not cache specific items.
You'd think so, but you would be surprised how quickly this adds up to other details people share, like "oh I just drove 15 minutes to get Starbucks" or something to that effect, small things that eventually add up to a precise location over time.
Yes, but if social engineering is involved and tracing back through user conversations across a platform, it's hardly a vulnerability, let alone one deserving of a bounty. The way this is currently functioning is intended functionality, and can be further locked down depending on the user's threat model.
This can essentially be classified as opsec failure for the Signal user. If they're trying to hide from a hit in a 300 mile radius, they've got bigger problems to worry about, and should already be using a VPN setup.
Every time you click on a link your external IP addresses is exposed, is this a vulnerability? Being online without a VPN / proxy is inherent consent to have your external IP & other required items to be shared with services / middlemen.
When it comes to Discord, if you have this strict of a threat model and you're still using it, idk what to tell you.
> opsec failure for the Signal user
Signal's mission is to provide security for users who don't know the word 'opsec'.
This "vulnerability" requires the user to have none of the normal things a person with a more extreme threat model would have already configured. EZPZ guides online on locking down Signal.
It's just like an iPhone. They don't ship with Lockdown Mode enabled by default, as it hurts the average consumer's usability. Signal at minimum will ensure no one is snooping on your messages, and it's up to the user whether they want to take that further.
If your definition of not providing security is allowing someone to know they exist on a continent, then that user's ISP has performed terribly as well since they aren't bouncing their signal around the world by default.
At least we agree about your argument. :)
> Signal at minimum will ensure no one is snooping on your messages, and it's up to the user whether they want to take that further.
Signal also secures metadata, including the participants in the conversation. That is undeniable - they have gone through considerable development investment to provide that feature.
> that user's ISP has performed terribly
Now we're blaming the ISP. If your app doesn't work with your users and ISPs, who does it work for? And how does a non-technical end-user know whether or when to trust you?
The fact that a user's IP is exposed when they click on a link is only relevant to the original post if a user would do this automatically and without realizing. The original post alleges that they can send someone a message on Signal and have the user automatically and somewhat unknowingly load a resource from a server. Sure, the author doesn't claim they have much control over the resource or the server, but they do show how you can check which server the user accessed and how that leaks information about the location of the user to a certain extent.
I mean, you just never know... I've seen a lot of wild things, I've seen what drives people to doing crazy things. Just look up the "Deadly Runescape E Dater" who flew from the US to the UK to stab the girl he e-dated.
If I host an image on Cloudflare and put the URL here, I'll know which CF datacenters are near HN users who bother clicking the link as well.
Whatsapp has this option and I'm pretty sure it is in privacy settings.
I imagine if one really wanted it to be view-once, it wouldn't go to a CDN.
Thanks for pointing this out!
Repeated applications of this attack (maybe disguised somehow?) could let you track someone’s travel over time, and it is usually only takes 4-5 zip code sized locations to uniquely identify someone.
The method that both Apple and Cloudflare use in their own privacy software (iCloud Private Relay for apple, WARP for Cloudflare) is specifically based on the idea that your region is not information that reveals your identity. If you enable Apple Private Relay, your origin IP will be obscured but the IP your traffic is routed through will be in the same country -- same principle.
https://www.apple.com/icloud/docs/iCloud_Private_Relay_Overv...
This attack is academically interesting and novel but it's not "deanonymization".
Yes unless Apple is doing Apple things and ignores VPNs for things like push notifications…
E.g. imagine sending otherwise anonymised participants in a clinical trial a questionnaire, containing an image. The owner of the image could then partially deanonymize the trial participants. Or voters. Or demonstrators in a rally.
Not everyone who cares about privacy is Edward Snowden material.
Now you’re no longer “within 250 miles,” hell my phone geo IPs everywhere from Louisiana to New Jersey , which are not even “in my time zone,” but there you go.
This setting was pissing meta/Facebook off big time because they also couldn’t narrow me down to a precise geographical area, resulting in much nagging and whining about “was this you signing in from [shreveport]?” and frequent account lockouts , password resets, and endless requests to approve my logins from a device that’s already logged in before I finally said to hell with it and deleted FB a few days ago.
I figure if a privacy setting makes meta mad , then it’s .. probably … a good setting. Must really irk them trying to sell location relevant ads when my state changes every other time I unlock my screen.
It’s a combined behavior of using private browsing and refusing to install their app, thereby giving them a permanent supercookie no matter what my IP is, so if you don’t like the sound of this it [might not] affect you if you use their apps. “X” does it too, just look up “inferred identity+ twitter” on google.
I’m editing out a tall claim in the last paragraph of this for some other time when I’m less tired and have sources next time we’re on the subject.
(It definitely may not be him and might instead be a random early user. But I think there's a moderate chance it's him.)
Details: https://news.ycombinator.com/item?id=29728339
(I don't advocate attempting to find and publish his name and address, since it'd make his life difficult, but it's still very interesting in the abstract as a curious unsolved mystery for all these years despite the number of eyes on it.)
So the target is somewhere in the many thousand square miles in the circle that encompasses almost half the US!
Which Cloudflare POP I hit depends on which RSP I use. In the country I live in, our biggest RSP peers with Cloudflare in a neighboring country (as it is much cheaper for Cloudfare to send traffic via that RSP's peering exchange there). So something like 40% of traffic will seem to be from a entirely different country than reality.
My RSP is a small RSP which until fairly recently only had two POPs in the entire country. So regardless of where you lived, customers of my RSP would have traffic exiting onto the internet via only one of two exit points. Rural users would seem to be coming from one of the two largest cities in my country even if they are easily >250miles way from their particular POP. They do peer with Cloudflare but obviously only at the locations where they and Cloudflare are in the same city (and I'm not sure this is the case -- it is possible all national traffic to Cloudflare traffic actually goes via the one POP in our biggest city).
The only reason this attack identifies the city I happen to be in is because I live in the same city as my little's RSP's biggest POP and Cloudflare happens to peer with that RSP at that POP. Where I am is a large city so doesn't narrow things down very much -- but even worse is that whoever is looking for me would actually need to look anywhere in my country.
I don't think I am an unique case as internet routing is rarely the most direct path for various technical, financial, political, etc reasons.
De-anonymization is definitely stretching the reality of what this 'attack' is capable of IMHO.
Even for individuals in those large, developed suprastates, it opens the door for catfishing and other social engineering approaches.
I can only assume this is a consequence of modern social media having shifted the Internet from being a bunch of pseudonymous people making and sharing stuff, to everything being myopically focused on one's identity first, and what they do second (as is literally the case here).
And it looks like it works to achieve its desired effect, too—a significant portion of the comments here are congratulating the guy for doing such a thorough technical write-up, given his age. Maybe this is just me being a grumpy “old” man now, but I would've found that condescending when I was his age, and would've rather concealed my age than be condescended to as such. But, to each his own, I suppose.
An anecdote - I used to be the lead for an infotainment security program for a well known manufacturer. They would send me to a lot of small security meetups and training. One in specific was a security training event for some HS students, which I would define as gifted. There were roughly 40 of them, from 14 to 17 years old, and they were all extremely impressive in things ranging from reverse engineering applications to assembly code all the way Linux systems stuff.
Something like this would have been easy for them - I mean the basics of this is that the attacker sends a message to a discord/signal user and then sends a request to a Cloudfare server. Not exactly splitting atoms IMO. What I think is special about this 15 year old in question is the epiphany that it might be possible and then giving it a go. This is the true hacker spirit.
I think after being exposed to so much internet, you realize how many are simply living a fantasy. In me it provokes a sense of disgust, I see it as part of a broader groomer problem on the internet, but this is a distantly minority take.
First dismiss it and see if the problem is still there in the morning. Hope that before then, someone finds a reason it's not a problem. Anyone?
I would even expect that Signal wouldn't allow you to download it more than once, and would immediately delete it after the first successful download. Well, ok, maybe the client fails mid-way through, so allow some grace period for a re-download. But I can't imagine that would be the common case either, and so disabling caching on their CDN would fix this issue, and hopefully not increase their costs much.
At any rate, "deanonymization" is a bit clickbaity here. Narrowing someone's location to within 250 miles or so isn't great, but it doesn't deanonymize them.
Edit: I didn't think about the case where an attachment is sent to a group chat, where multiple people will be downloading it. But in that case wouldn't the attachment be encrypted individually for each person in the group? I'm not sure how this works, of course.
The items you mentioned can essentially be configured, for those that want the insane level of privacy / security. Messages can be auto-deleted 30 seconds after being seen, a proxy can be configured to route all your traffic through it, and tons of other things can be done to customize it more to the user's liking.
I'd imagine they're caching it because of egress costs. File attachments, voice mail, video, etc. can all add up.
If images/attachments were e2ee, this problem probably wouldn't exist, right? or are the images on cloudflare encrypted?
Edit: I should clarify. I didn't mean the encryption itself fixes the problem, but rather that: If this were handled like the text messages we send (not via cloudflare CDNs) then this wouldn't exist. I get that attachments are quite some bytes bigger than text but shouldn't the security guarantees be the same?
It seems that signal is indeed encrypting all attachments and therefore the encrypted attachments are cached and served via CloudFlare.
So, I'm guessing the images are encrypted where they're stored. And from his post it sounds like it doesn't happen with the messages, so the motivation for using CloudFlare probably is around egress pricing, or they could be using CloudFlare R2 for storage as well.
And that bug report to Adobe was made when they would have been five years old: https://hackerone.com/daniel?type=user
as you said, impressive and insightful. :D kinda feel like the docs on it were a bit chatGPT aided, they are super clear and full of 'certain sentences'. (this is totally an excellent use-case for that, so not bashing on it at all!).
nice read.
If someone sends you a youtube link and you hit play, YT knows who you are, both from a network perspective and potentially the logged in user.
If you are using signal in a high risk environment, you should be using it from a system that contains no extra information about you. This is the same posture one should take when using Tor.
Basic opsec.
I don't think these kinds of things are in signals threat model. It is meant? as a message platform for people with nothing to hide?
opsec is _incredibly_ hard for a person not deeply into technology and this type of information. you might argue that you need to stick with certain tools and techniques that are known good, but new vulnerabilities and techniques implemented against you can completely shatter previous knowledge on whats good and bad opsec and still break it despite doing it 'very well'. (like certain darknet markets being closed down due to new vulnerabilities being found in the platforms they use...)
most people who rely on opsec/tradecraft for a living, also rely on teams of people to help them maintain it and validate it constantly... (or eventually fail and get bitten).
you are right though that its unlikely a company or app producer would have a threat model tuned to people who want to hide stuff. those things generally tend to be closed down sooner or later. (encrochat and such services...)
This means, never using a browser context you have ever logged into any service that is personally identifying. That also means the order in which you load pages. If your ritual is open pintrest followed by slashdot, that is now your finger print.
It isn't just what you do, but how you do it and the ordering between those events. You also don't want to accidentally deanon yourself or your peers, even when everyone is trusted because it also leaks group membership information.
The mental framework for opsec can be modeled as vector calculus and differential geometry. You have to think of the flow of information across a surface and in the integral of that flow. Assume an adversary with perfect total information.
For example, connecting to a VPN and checking https://cloudflare.com/cdn-cgi/trace gives me `colo:CPH` (Copenhagen) which is far from my nearest CF datacenter (geographically), closer to the IP location from my VPN provider (Oslo) but still not particularly close?
If I don't use a VPN, I don't even get the capital city of my country (which I'm in right now), I get a colo approx 250 miles north. So I also dispute that Cloudflare always returns the "nearest available datacenter".
Don't get me wrong, the write up is cool and certainly interesting - just not convinced on the real world applications here...
It's less accurate than that. IP Geocoding can be down to the city level in many cases. This is _maybe_ nearest cloudflare data center
As a piece of data alone, the results are probably not of significant use.
The real-world application (and potential danger) is when this data is combined with other data. De-anonymization techniques using sparse datasets has been an active area of research for at least 15 years and it is often surprising to people how much can be gleaned from a few pieces of seemingly unconnected data.
That's exactly the point. In this case it's only really possible to de-anonymize people who take long distance trips. But based on two data points it might be possible to know which flight or train a person travelled with.
With three different data points it might be quite unique. For example you might find out somebody travelled from Italy to Norway on Monday evening and then to France on Wednesday morning. There are probably not so many people who did a trip like that, it might come down to only one (or a handful) people who fits this itinerary. With other data sources it might be possible to uniquely identify this person.
Seems pretty handwavy. Can you describe concretely how this would work?
It has a whole Wikipedia article and everything.
https://en.wikipedia.org/wiki/De-anonymization#Re-identifica...
>Can you describe concretely how this would work?
Here's one of the earlier papers I remember off-hand, demonstrating one methodology. New (and improvements to existing) statistical techniques have happened in the ~18 years since this was published. Not to mention their is significantly more data to work with now.
https://www.cs.utexas.edu/~shmat/shmat_oak08netflix.pdf
"We apply our de-anonymization methodology to the Netflix Prize dataset, which contains anonymous movie ratings of 500,000 subscribers of Netflix, the world’s largest online movie rental service. We demonstrate that an adversary who knows only a little bit about an individual subscriber can easily identify this subscriber’s record in the dataset."
From the Wiki I linked:
"Researchers at MIT and the Université catholique de Louvain, in Belgium, analyzed data on 1.5 million cellphone users in a small European country over a span of 15 months and found that just four points of reference, with fairly low spatial and temporal resolution, was enough to uniquely identify 95 percent of them." [...] "A few Twitter posts would probably provide all the information you needed, if they contained specific information about the person's whereabouts."
Point being that operational security is hard, and it takes a lot less to "slip up" and accidentally reveal yourself than most people think. Obtaining a location within 250 miles (or whatever) can be a key piece of information that leads to other dots being connected.
Other examples (albeit with less explanation) include police take downs of prolific CSAM producers by gathering bits and pieces of information over time, culminating in enough to make an identification.
> [...]
"Researchers at MIT and the Université catholique de Louvain, in Belgium, analyzed data on 1.5 million cellphone users in a small European country over a span of 15 months and found that just four points of reference, with fairly low spatial and temporal resolution, was enough to uniquely identify 95 percent of them." [...] "A few Twitter posts would probably provide all the information you needed, if they contained specific information about the person's whereabouts."
The only reason the two attacks work is that you have access to a bunch of uncorrelated data points. That is, ratings for various shows and their dates, and cellphone movement patterns. It's unclear how you could extend this to some guy you're trying to dox on signal. The geo info is relatively coarse and stays static, so trying to single out a single person is going to be difficult. To put another way, "guy was vaguely near New York on these dates" doesn't narrow down the search parameters by much. That's going to be true for millions of people.
That's why I said that this data alone is probably worthless, but can gain value when combined with other data.("As a piece of data alone, the results are probably not of significant use")
The combining of data is the important bit and the entire emphasis of both of my other comments.
Two pieces of otherwise anonymous data can, when combined, lead to re-identification.
How are you going to get more anonymous data? Practically speaking if your target has such poor opsec that he's hemorrhaging bits of data, you probably don't need this attack to deanonymize them.
All over the place? Your comment history here (and mine!) is full of data. Each piece alone isn't identifying, but there's a good chance that in aggregate it is.
If you share that username on discord/twitter/reddit/steam/whatever, that's even more data. If you reference old accounts anywhere, you guessed it, even more.
>you probably don't need this attack to deanonymize them
My comment wasn't necessarily specific to this attack, just noting that this attack can be an additional piece of data in the chain of re-identification.
You've gone from "not convinced on the real world applications here" to "how are you going to get more anonymous data". If we assume that you can get some data somewhere (a small list of example sources above), can we agree that there is, possibly, a real world application?
There is a reason applications go to so much effort to proxy requests to resources such as images. It's not free to do this.
And I strongly disagree that being able to uncover somebody's rough geographic location is not a privacy problem.
I wouldn't be surprised if this, for example, lets you deduce if somebody is currently home, at work, or commuting (as all three ISPs might be hitting different Cloudflare datacenters). That's not information everybody is comfortable broadcasting to the world.
> Privacy isn’t an optional mode — it’s just the way that Signal works. Every message, every call, every time [1]
While I don't consider this a critical bug requiring an immediate technical remediation from Signal, this should definitely be either fixed or called out in the documentation at some point.
[1] https://support.signal.org/hc/en-us/articles/360007320391-Is...
> Signal conversations are always end-to-end encrypted, which means that they can only be read or heard by your intended recipients.
They're not saying that it is an anonymisation proxy, they're saying the messages and calls are encrypted for the recipient rather than to the server
My closest Cloudflare CDN is just listed as "DFW". The DFW metro area is about 8,700mi^2, and I imagine I could be even further than the "metro area" and still get the "DFW" Cloudflare datacenter.
In their little video animation, the area inside the overlap of those two circles encompasses several states. The edges of the two circles go from Washington to Florida and almost include Chicago. The target could have been in Denver or St Louis or Las Vegas or Phoenix or San Diego or San Francisco or Amarillo or El Paso.
And then this whole thing gets thrown off if one uses a VPN with an endpoint somewhere other than where you are. Click a button, suddenly my datacenter is AMS. Click it again, suddenly its OTP...
Discord is just an example, this can apparently work with many apps that store user attachments on Cloudflare.
>Click a button, suddenly my datacenter is AMS. Click it again, suddenly its OTP...
Well, if the location keeps changing, it's obvious it's not their real location. But if it’s always the same, no matter what, that’s a huge clue. Of course, this works best when you’ve got some other data to back it up. It’s kind of like playing Akinator - the more answers you get, the closer you get to figuring out the target. One answer might not tell you much, but three or four?
(It's still an interesting vector, though! But it's true that the headline and writeup are a bit sensationalized.)
Assuming local client-side caching, the total number of requests for that resource should be very small, probably one in the vast majority of cases.
On an unrelated note, it seems like CloudFront could very easily fix this by not returning the cf-ray header, or at least having an option for the customer to remove it. Although, it might still be possible to get that information based on timing information...
The Cache-Control http header has a `private` directive specifically to inform CDNs and similar not to cache the response.
Then you just look at the response time. If the resource needs to be fetched from another continent, this is probably reliably measurable
Same for websites trying to hide which users exist: do a login request for an existing username and it'll do the password hashing (usually adds at least 50 ms to the response time), whereas for an invalid username it early exits. The fix is to always run the same code, so always do the hashing, which very few sites do. (Or not care about revealing this and telling people straight out that their username is unknown, if that fits with your threat model.) So to get back to Cloudflare's case: it won't help unless they delay responses, which is the opposite of what they're supposed to do
But any user can send anyone other user a message that includes a link to a CDN-cached resource. Isn't that the "attack" here? Or am I misunderstanding?
"For that server" is the other number-of-requests..
Theirt defaults are set so they can get mass market addoption, whilst beeing a big step up in privacy compared to the usual players in the space (like whatsapp and telegram). You simply won't be able to get the average user on apps that make use more complicated and apps like simplex doe exactly that.
If you want Signal to be more secure, you can circumvent this attack vector by disableing auto downloads for media.
I'm not saying Signal is perfect, there has been a bunch to critisize over the years.
But why argue about use cases they never claimed to solve?
At the very best, they are weakly pseudonymous, but that's about it. And yes, loading media by default has always been a staple of applications who prioritize their users' convenience at the expense of some security, a fine choice for the usual threat model of their users. And embedding media in messages has always been a staple of deanonymization attacks.
So ok, the tracking pixel has been shown to still be a relevant technique today, that's nice but not surprising.
If you want to remain anonymous though, don't use Discord or even Signal, and I'd advise against posting on HN either. Maybe, if you automate the pasting of messages (no js!) that has been reworded by a local llm from throwaway accounts through whonix, at random times that can't be correlated to your timezone, you _might_ have your chances. Don't bet on it.
Anonymity does not exist any longer.
* Funny enough, not vulnerable this time because they use an in-house protocol, which is maybe even worse.
I don't understand how Signal could dismiss this so easily. I'm starting get a bad feeling about their responses to these "low" stakes attacks. They already missed the ball on the database encryption mishap on desktop.
If you don’t want people to be able to detect your rough geographic location, you should be using a proxy to hide it. For everybody else, knowing the edge server you are closest to is really not a threat.
If wishes had wings, sheep would fly. People who want their computer to do a certain thing can also be expected to do a quick web search for how to make it do said thing. E.g.: hiding location? Use onion routing. Signal doesn't claim to hide your country (heck, they require your phone number!) so it seems wishful thinking to say they should have included e.g. a Tor client and enabled it by default
The same information would then be available in the timing, but given the distributed nature here, that would be a lot harder to pull off.
The section "How to Protect Yourself" is lacking.
Step 1. Don't receive this information in the push message. Only send the fact that there is something waiting for you in the app. Chances are there are other vulnerabilities that compromise the end-to-end encryption guarantees provided by the app (and only by the app).
In Signal on iOS: Click on your icon in the top left corner. Click on settings. Click notifications. Click on display below "message contents". Make your choice.
Another situation where convenience clashes with security, unfortunately.
Its quite bizarre why social media apps allow anonymous people to interact with you. 99% of the conversation I have is with people that I roughly know.
No extra work for person A, and the work for person B is just what person A had to do anyway.
Bit strange to attribute this to 'social media apps', isn't it? I'm interacting with an anonymous person right now. Most platforms allow it, including the older ones (i.e., IRC)
I mean, it's one of Discord's major use-cases. Joining a server of a common interest and meeting/talking with other people that share that interest.
>anonymous people
Wtf, how is this even relevant?
You know them from somewhere else, lets say I play a game and we decided to get into a voice chat. We could create a temporary, dynamically created voice chat that we can all join (much like Google Meet) where all of us are anons.
Then, if we really want to know each other, we can then share the UUIDs.
I understand why ANYONE can send an email to me (I can decide when/will to check them)
I don't understand why ANYONE can whisper to my ears (I cant decide since they are pushed to the top of the app)
If the message is from a known or trusted contact, I think there can be larger problems than just a rough location reveal.
Usability, most likely. Ultra-secure and paranoid doesn't result in good UX most of the time.
I guess you went through the post too quickly, because it goes over how that's exactly how it works. Unless you have push notifications enabled and on default settings to include the content in the push notification.
Where are you getting the impression that signal auto-downloads attachments from an unknown number/contact? The OP says there's auto-download, but not that it happens from unknown contacts.
It seems that time and again, security-enforcing procedures assume that many functions they invoke are pure, but in reality these functions have side effects, and these effects are observable much easier than the security requires.
The actual problem here that the secured area is only the stuff that came through the encrypted channel. Any access beyond it, like following a link, is obviously insecure. If the link was sent via the secure channel, it becomes even less secure because it allows to observe a correlation between the secure channel (otherwise impenetrable) and the insecure outside context, and allows to blow (some of) the cover. Opening links via Tor would mitigate it a bit.
The hard truth here is that almost everything may have observable side effects, so opsec needs to permeate all aspects of life, the more cover you need, the fuller. This is mostly incompatible with a convenient UX, but, to be popular, a secure messenger has to be reasonably convenient. This necessarily limits the level of security attainable by its casual use.
[Spectre]: https://en.wikipedia.org/wiki/Spectre_(security_vulnerabilit...
For many commenters, it looks like deanonymization means unveiling highly sensitive info like name, address, email, etc.
For privacy-conscious individuals and hackers, it looks like it means 'revealing a data point that shouldn't be revealed'.
As a signal or Discord user, I would expect my country location not to be revealed to a person I don't know. So the latter definition makes sense to me.
For reference, here's a 250 mile radius around Toronto Canada https://i.imgur.com/ydpR0IZ.png
Otherwise, they wouldn't pad attachment and message sizes, offer a "sealed sender" feature, allow relaying all calls to avoid callers/callees from learning users' IP addresses etc.
MAYBE some forum doxxed users by posting their informatio? but I didn't see any.
I don't know about the UD bit this will not be very accurate within the EU.
As an example: In Hungary, there's pretty much only one peering hub (bix) and there's only one Cloudflare datacenter. You've already geolocated me better than this hack just by knowing my language or phone prefix.
In my case, Cloudflare will identify me as BUD even when i'm roaming at a different country.
This behavior is very typical for the EU, because the telco landscape is fairly fragmented, and each company typically have only one, or at most 2 peering locations.
This may be different within the US where the distances are bigger, and latencies matter more, so there is more incentive to peer locally.
It's nice but at most will give you an indication of city. Perhaps together with some additional OSINT you could find the user but you'll need a lot more clues.
Well found though!
This changes the attack from a 0-click attack to a 1-click attack.
That could be as simple as adding some extra pseudo-random parameters to the URL which will be ignored by the origin (but honored by the caches), or as complex as creating a completely separate URL for the receiver of the message, and somehow giving it to the receiver without giving it to the sender (easy on Discord, harder on Signal due to its end-to-end nature).
But it would solve the issue completely because you could always check the response time. Probably Signal should disable caching. I guess it's rare for someone to repeatedly download an attachment. Once it's there it's there. For grouped conversations it could be an issue though.
Basically this allowed an attacker to find out which cloudflare data center a victim connected to when being tricked into loading something from cloudflare. This is often within a 250 mile radius of where they're living but not necessarily.
Can't one find out someone's IP just as easily by making them make a request to a URL controlled by an attacker? Is the problem that cloudflare is whitelisted for 0-click?
Unless you can find another flaw in Signal, that'd likely be a 1-click attack, which is less valuable than the 0-click attack demonstrated by the author.
Example you used the normal Signal app without patch and sending me a message, and I have the patched version.
Just to remove certificate pinning, to be able to see the API traffic because of encryption.
Without this control over the route (driving the probing of which caches were hit), the attack would no longer work, right?
However, Cloudflare are known for being harsh on VPN exit points and the behavior of requesting the same (unique each pass) image from every geography and then never again, would probably look significantly suspicious, but yeah it seems not to be a priority for cloudflare at the moment.
Why is that even the case? I had understood that (binary) attachments are embedded into the encrypted message and hence transferred directly from sender to receiver.
Obviously, retrieving media from an external location saves bandwidth at multiple positions. I am not a security expert, but it seems almost trivial to see how storing message data on an external server conceptually facilitates attacks like this one. Isn't that the same reason a link preview is generated at the sender first and then embedded into the message as an image?
Would also work without anycast (and thus probably able to use a very dense botnet) and long list of NS entries for your domain.
This will be more accurate than the cloudflare approach.
1. Attacker sends novel image to Signal
2. Signal hosts the image on their core servers
3. Signal instructs victim to fetch preview of the image
4. Victim asks the CDN for the image
5. CDN gets the image from Signal core servers and caches it
6. Victim gets the image from the CDN and displays the preview normally
7. Attacker hits every one of the CDN cache servers
8. The CDN cache server that say "yep, saw that already" is the one closest to the victim
This is assuming the data center is directly requesting the source server which it might be given a few searches on Google [1].
[1] https://community.cloudflare.com/t/cloudflare-is-forwarding-...
It's obvious in hindsight, but I bet no one would have mentioned this possibility as why you should disable notification previews or that simply receiving a notification would possibly reveal this information.
Can one disable those features in Signal? Would be annoying becuase they are nice, but yeah.
If you don't want that attack to be able to locate you somewhat (or at least locate your internet endpoint, if you are using a VPN or something), you will need to turn off signal previews and network image displays. Right?
CDNs do not choose datacenters for users based on a geographic distance. The number one metric is latency but latency != physical distance. Second metric is optimizations of price of data transfer between peers and IXPs which results in very dynamic routing rules. Then consider also network/software hickups/maintanance and distribution of datacenters' load...
It's "a very rough estimation of a user's location when they are not using a vpn".
This only works because the attacker knows the URL.
- The information extracted is a rough 250 mile radius around the user
- The attacker already has a way to contact the person (signal username / phone number)
Intersting reading, but also seems like technical clickbait.
Within ~250 miles of their location is not "incredibly precise"
For example: Jami - one of the most feature-complete, distributed IM...
That's my 0-click deanonymisation.
Nice attack otherwise.
And you could be falling into his trap of getting you to believe so by expressing distance in miles, as well.
I use alpine (the email client, not the Linux distro). Before that, I used pine.
Every single thing that gets loaded from anywhere on the Internet has to be the result of an action that I take. Nothing ever gets loaded automatically. I get to choose if I load the thing using the server that I'm connected to, or if I load it directly on my local machine. I know the implications of each.
The fact that programs, particularly ones that are supposed to be for the security minded like Signal, load anything by default, automatically, is just, well, naive.
I can't be the only person who thinks that people who don't think these things through shouldn't be working on apps and email clients. Sure, people would have a cow if their email client didn't load every frigging thing and run remote Javascript and so on, but in Signal? Really?
(end rant)
I see that this can be turned off. I will now tell everyone I know that uses Signal that this should, in fact, be turned off.
I can't even convince what the gouvernements are able to do. You could technically route signal over tor network but then even tor has vulnerabilities with it's C coding.
The speed of light is the main culprit here.
is there any good reason for deciding this way on the part of Signal et al?
But that wouldn't help anyway, even if the image could be cached near the sender first, or the signal server prewarmed some other cache. After the victim opened the image, the attacker would see two locations that have the image cached, and could easily deduce which one is the victim's location (e.g. if Signal pre-warmed a random cache, repeating the attack a couple of times would be enough to eliminate the randomness).
even matrix encode image and other data in the e2e p2p message flow
Hardly.
Amazing sleuthing but not deanonymization.
very much disagree on this, they track mobile devices through your connection strength to multiple cellular towers while this attack proves which singular datacenter the victim is nearest.
Don’t get me wrong the write up is really interesting but it does feel like the author is a bit of a sensationalist.
Extremely sensationalist. A cell tower might have a range of a few miles, max. This is giving ranges of 250+mi.
They claim to be 15 years old. Cut them some slack.
what have you made lately?
So what are we supposed to do? Dox him, find who his friends are, and use them to backchannel feedback? I think the "sensationalist" critique is direct and actionable - just don't do it.
And I think expecting that all criticism must come from people the target of it knows and trusts is a bit much.
> what have you made lately?
Plenty of stuff. But that's irrelevant. People are free to give feedback regardless of what they've been working on.
> Joined November 2017
so likely a bit older :)
So either they lied about their age then in order to join social media and they're some sort of child prodigy... or they're lying now.
Benjamin Dover, 1600 Pennsylvania Ave, born in 1999 ;)
"Telegram, another privacy-focused application, is completely invulnerable to this attack"
"Discord […] citing this as a Cloudflare issue other consumers are also vulnerable to"
"Cloudflare ended up completing patching the bug"
I wish Signal would react differently. I still remember the bubble color controversy when they changed their mind after the backlash and not before. :-)
I understand that Signal does not consider this
https://gist.github.com/hackermondev/45a3cdfa52246f1d1201c1e8cdef6117 to be
a valid security bug, but it would be helpful to at least be able to
mitigate it.
Please add an option in settings to disable automatically downloading
attachments.
That should be enough to change the attack from 0-click (just opening the
conversation) to 1-click (click the attachment). Most people won’t care
about this, but for some every little bit of privacy is important.
" You can disable the auto-download. Settings > Data and storage > Media auto-download, you can choose what to auto download for mobile data/wifi/roaming."
So, that part is there, but my question is, it's still aissue when they manually download the image, right? Unless something never accepts images from someone they aren't expecting, who 's number or unique created ID has never been seen before
Yes, this still an issue if you manually download an attachment, but that’s a lot better than automatically when you open a conversation.
This short quote fragment is a little misleading: Cloudflare patched the bug in their systems that allow you to send HTTP requests to any CF data center, regardless of where the originator of the request lives. This is likely something they want fixed for a large variety of reasons, some probably much more important than the specific attack OP wrote about.
> I wish Signal would react differently.
The severity of a potential security issue, or the determination of who is responsible for fixing or mitigating it, is a matter of opinion. Just because you think this is important for Signal to fix, it doesn't mean it's some absolute truth that it does. At the risk of appealing to authority, I would expect that people who run a security/privacy-focused messaging project to have a better handle on classifying these sorts of things than random people on HN like you or me.
But of course, sometimes they'll get it wrong too. I'm not familiar with the bubble color thing you mention, but sure, nobody's perfect; we're all human and we make mistakes. I'm personally not convinced Signal needs to do anything here. A 250 mile radius is quite a large area, and users can already choose to not auto-download attachments. To be fair, though, I think a simple way for Signal to fix this would be to disable caching on the attachments HTTP endpoints, though that might increase their bandwidth bills and increase load on their servers, depending on what their access patterns look like.
https://yasha.substack.com/p/signal-is-a-government-op-85e
https://www.kitklarenberg.com/p/signal-facing-collapse-after...
https://www.city-journal.org/article/signals-katherine-maher...
https://drewdevault.com/2018/08/08/Signal.html
https://bigleaguepolitics.com/court-docs-show-fbi-can-interc...
> There's clearly a problem here as Cloudflare says consumers are responsible for protecting themselves against these types of attacks, while consumers (ex. Discord) are putting the blame on Cloudflare.
>I wish Signal would react differently. I still remember the bubble color controversy when they changed their mind after the backlash and not before. :-)
Can you blame them though? They're a non-profit with limited manpower and resources. There's quite a lot of cranks in the security field, and as many people have echoed in this thread, the bug report is rather sensationalist. At some point you just have to pattern match and ignore any reports that seems a bit too cranky. Is this ideal? No. But I don't see how it's any different than summarily dismissing a vaccine skeptic's claim that vaccines are bad, even if there's a kernel of truth buried in there (eg. that benefits for young people are questionable).
I was already on the "I just want to be left alone" vibe generally before all that happened to me, so I just carried on as usual.
But calling this de-anonymization is a stretch, if it can possibly pinpoint you within 250 miles (that's assuming geoip is correct too, which it rarely is).
In their GeoGuesser demonstration video, the higlighted area is densely populated and you still would need to match millions of people vs the online user.
It does provide some hints as to the location of the targeted user, and that is cool!
The list of suspects would be fairly small when US officials cross-check individuals that travelled US-UK on Jan 4 and Germany-US on Jan 21.
If the scammer is in Nigeria, tough luck. If he is in the EU or US then exists a feasible chance to go after the person.
It's not using geoip, it's using anycast.