Tor Open To Attack

An anonymous reader writes "A group of researchers have written a paper that lays out an attack against Tor (PDF) in enough detail to cause Roger Dingledine a fair amount of heartburn. The essential avenue of attack is that Tor doesn't verify claims of uptime or bandwidth, allowing an attacker to advertise more than it need deliver, and thus draw traffic. If the attacker controls the entry and exit node and has decent clocks, then the attacker can link these together and trace someone through the network."

Re:Not quite so oblig SW reference..

[Ice Wewe]

Seriously, this is why Tor tells you at the start that you shouldn't rely on it for strong anonymity.

"Feb 25 16:16:02.628 [notice] Tor v0.1.1.xx. This is experimental software. Do not rely on it for strong anonymity."

Thus proving, once again, that Tor is only for the Quasi-anonymous group.

Could this be avoided?

[DogDude]

From what I can tell, it sounds like an attack can be either minimized or avoided completely if there are enough "server" nodes in the network. The "server" nodes, or the nodes that are exposed to the potential naughtiness, are always in short supply due to people understandably not wanting the FBI to show up to their door, hauling them off to Guantanamo Bay for a round of government-sanctioned torture. The thing is, for the time being, we're seeing a proliferation of completely open (untraceable) wireless networks that could potentially solve this problem. If a relatively large number of geeks were to throw a machine at their local free wireless connections, then they could potentially help out the TOR network for people who don't have access to such an "open" network. Now, we will eventually see these wide open free-for-alls shut down once the feds get their heads out of their asses and start taking Net-based crime seriously. But for the time being, we should all pitch in and take advantage of these networks while we've got 'em. I'm working on putting together a few Frankenstein PC's now and they'll be sitting within range of my town's wireless network, and they'll be routing TOR traffic. If somebody does some truly nasty stuff, and it comes out via one of my TOR nodes, then all the federales will be able to see will be the MAC addresses of my network cards, and have no idea where to find said network cards on the wireless network.

Re:Well, not just that.

[TubeSteak]

If the attacker advertises absolutely massive values (and hey, it's only a string) they can time out all of the packets and DoS the network too.

Wouldn't that only last as long as [max client timeout]?
At which point the client seeks another route. Right?

What I'm saying is that I don't think this would be effective with only one or two nodes.
Though on a larger scale, I agree that this tactic could effectively DOS the network.

Re:Could this be avoided?

[kennygraham]

then all the federales will be able to see will be the MAC addresses of my network cards, and have no idea where to find said network cards on the wireless network.

Unless you purchased your network card on a credit card at a place that scans the MAC address along with the UPC when they ring you up, like CompUSA does. (to make sure you don't return a different network card for a refund)

Re:Well, not just that.

[Wonko the Sane]

The military and secretive NSA operations do not care about you or your open source proxy software. Stop trying to make yourself feel special by writing convoluted conspiracy theories.

If [dailykos.com] only [commondreams.org] that was true [sldn.org]...

Re:No love for Freenet?

[makomk]

A casual googling didn't reveal anything, and I'm feeling really curious about how that happened.

As the above AC said, a lot of the discussion was on Frost, which doesn't have any publicly-accessible archives. You can find the mailing list thread here [freenetproject.org], though. In particular this [freenetproject.org] and this [freenetproject.org]

Of course, I'm not sure if this really matters that much; last I heard, Freenet was known to be vulnerable to man-in-the-middle attacks [freenetproject.org], and fixing it wasn't considered a priority...

Re:How Many Nodes Do You Need to Own?

[mrogers]

That's fine for small networks, but for a network with hundreds or thousands of nodes, controlling 5 to 10 percent may become infeasible.

Tor scales to a few hundred nodes [noreply.org], but it doesn't scale indefinitely - all the routers are listed in a central directory [seul.org] to ensure that all clients use the same set of routers and the same set of public keys.

Official Tor response

[shava]

Please check out http://blogs.law.harvard.edu/anonymous/2007/02/26/ the-rumors-of-our-demise/ [harvard.edu] for The Tor Project's official response to this paper.

Shava Nerad
executive director
The Tor Project