Hot answers tagged

9

Let's start with a minor correction: there are only 9 directory authorities. You probably counted Tonga, but that's the bridge authority which is pretty much unrelated to the other 9 directory authorities. (Discussing what would happen if somebody took down the bridge authority would be, well, a separate discussion.) Now let's distinguish three cases: ...


9

Is the client able to detect a malicious bevaviour from an exit node? Not really. If a malicious exit relay operator conducts a man-in-the-middle (MitM) attack by using a self-signed certificate, TorBrowser will display a certificate error page. That's what everybody already knows from an ordinary Firefox. Right now, there is no easy way to distinguish ...


8

Short answer is no, not really. Timing attacks can be defended against by pumping a constant stream of data through the network. That's not foolproof, however, since an entry / intermediate node could introduce lag spikes which could then be analysed. I believe that high-latency anonymity networks (anonymous remailers) have all kinds of timing attack ...


7

The short version is: If you happen to be an entry node for a hidden service, and you connect to that same hidden service, you can tell you're its entry node (and what its IP is) by correlating the traffic you're sending to the hidden service with the traffic you're sending to a client (which is the hidden service). If hidden services didn't use guards and ...


6

"Does Tor still present a threat to the NSA?" I believe that Tor was never threat to the NSA. There are several layers of 'protection' about Tor, thus several ways to attack users. The first layer is: software code. NSA software developers can misuse open code to find holes and bugs in the code. We can surely make the presumption that the NSA doesn't have ...


6

To have your program use the Internet through Tor, just teach it to use Tor as a SOCKS4a or a SOCKS5 proxy. The Wikipedia page on SOCKS should have the information you need.


6

The short answer is no. Basically, Tor is susceptible to timing correlation attacks, where someone who is observing the connection going from your client (OP) to the Tor network and also the connection from the Tor network to your destination can tell with fairly high certainty that they are the same connection. Note that you would need to correlate data ...


5

It's arguable that few technologies, and none that are commonly available, provide stronger anonymity than Tor does. The NSA has called it "[t]he king of high-secure, low-latency anonymity". However, as user-friendly and secure as the Tor Browser Bundle (TBB) has become, it cannot reliably prevent tracking and identity correlation. Online vulnerabilities ...


5

While nickm's answer of "Use SOCKS, that's what it's there for" is correct, I think you might be asking the wrong question. If you want to get information about other aspects of Tor, but don't want to perform queries, implement SOCKS, etc. yourself, you can always use one of the existing libraries. In Python, for instance, you can use Stem. If you're ...


5

That's a tough one. Anyway, here goes my personal take on this story: We don't have any extra sources --- all we can do is read The Guardian's article or the one published by the Washington Post, like everybody else. Even though we have no way to be certain whether the documents referenced in the article are, indeed, genuine, I still highly recommend you ...


5

I don't think the Tor client itself can detect malicious behaviour carried out by an exit node nor should it. If you're browsing a site over http:// then as you say, the exit node can view and manipulate your traffic like any MiTM could. The solution is TLS but as you pointed out there are MiTM attacks that can be launched against sites using TLS such as ...


5

Making a movie available via BitTorrent is fine. But using Tor, either for seeding or recommended for downloading, is unwise. It's hard to properly configure torrent clients to use Tor without leaking, so recommending that people download via Tor would put them at risk. And even if torrent clients are properly configured, they would be stealing bandwidth ...


5

This is an ongoing attack on the Tor network. A group has established ~3000 relays (and growing), ~50% of network nodes (note, network nodes, not network capacity for which I don't have a decent measurement, but which is much smaller). However, as all of their nodes are fairly new, and some are being blocked by the directory authorities [1], the probability ...


5

Linostar's answer is on the right track, but missed the Tor version you specified. You should update to at least the 0.2.5.x series for Tor to try and detect out of memory situations and handle them smartly. I'd suggest upgrading to either 0.2.5.x or even 0.2.6.x if you don't mind an alpha to se what happens.


4

You are actually asking two questions here. One is about censorship resistance (can somebody block the bootstrapping process?) and the other about authentication (can a bad person pretend to be a Tor relay?). Here are answers to both questions: Censorship resistance: Yes, a nasty network administrator can indeed block the bootstrapping connections which ...


4

I believe it is possible, but don't know if required tools already exist that anyone could use with low technical skills. This answer will cover both traffic correlation and timing attack issues. My idea is, you must somehow be able to use some computer in the middle anonymously and send it commands to perform anonymous tasks on scheduled dates and times, ...


4

You need to accept that all things flowing through an exit node are most likely analyzed by big brother government. Everything you send must keep your anonymity. If you are deploying sensitive information, you need to use encryption.


4

While I don't have an expert answer, I can draft some thoughts on your first question. To estimate one's security level you have to define what your adversaries' capabilities are (technical skills, financial power, time and number of men), plus other factors (why would they spend their resources on targeting you, ...). That will form your threat model. ...


4

To manually set an entry node see the following FAQ entry: Can I control which nodes (or country) are used for entry/exit? Yes. You can set preferred entry and exit nodes as well as inform Tor which nodes you do not want to use. The following options can be added to your config file "torrc" or specified on the command line: EntryNodes $...


3

Yes, your privacy will be compromised. Please, don't ever rely on unencrypted protocols. This is also true when not using Tor. Your message will not be read. Also the E-Mail header (sender address, used mail software (usually containing version and operating system) etc.) might identify you, just like your style of writing. Your use case sounds like it isn'...


3

Identity correlation is learning that two or more identities -- Like Joe on Facebook and Aron on StackExchange -- are actually the same person. This can be a problem if you don't want others knowing this; for example, Aron is an anonymous gay rights activist, and he made a Facebook profile under a different name to avoid getting persecuted/trolled/flamed. ...


3

For a tutorial on client usage through tor see here. Stem is one of the most feature complete controller libraries, but there's certainly others available too.


3

To add to what's been said, particularly parts of bobrock's answer, remember that anyone can run a Tor exit node. After traffic has been decrypted on the exit node (as the last stage of onion routing), the data to be forwarded can be seen in the clear (assuming there's no more encryption besides Tor). The NSA can set up a large number of exit nodes, and ...


3

Exit relays will continue reading until circuit dies (in old versions) or buffer of a relay becomes too big (in new versions, intended to prevent DoS) . If you are a 'honest' client, the exit node will only make 1000 cells and then stop reading due to the hard-coded 1000-cell limit on sending window. So yes, it basically depends on something to the circuit ...


3

Lizard Squad was a pretty noisy sybil. We have monitoring for events of that sort... https://gitweb.torproject.org/doctor.git/tree/sybil_checker.py Naturally that event has sparked interest in more sophisticated sybil detection... https://lists.torproject.org/pipermail/tor-dev/2015-January/008156.html https://lists.torproject.org/pipermail/tor-dev/2015-...


3

What prevents a directory server from being dishonest and give malicious data to the user? The information served by the directories is generated by reaching a consensus between the authorities. You would have to control the majority of the authorities to manipulate the consensus. This should be fairly hard as they are neither under the control of one ...


3

No, and yes. Facebook, hidden services, and https certs had talked on this. Facebook in fact brute forced only the first 40 bits and then made a backronym. Their hidden service name is "facebookcorewwwi.onion". For a hash of a public key, that sure doesn't look random. Many people have been wondering how they brute forced the entire name. The short ...


2

I defer to Peter Palfrader's aka weasel's excellent answer to the main question, "How safe are Tor users?". Reading the closing sub-question, "Does Tor still present a threat to the NSA?", I'm wondering whether OP meant to say "Does the NSA still present a threat to Tor users?". The answer for that question is "of course". Regarding Tor as a threat to the ...


Only top voted, non community-wiki answers of a minimum length are eligible