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Attacking and Defending the Tor Network 132

Posted by CmdrTaco
from the takes-a-codpiece-and-a-helmet dept.
Trailrunner7 writes "In a talk at the USENIX LEET workshop Tuesday, Nick Mathewson of the Tor Project discussed the group's recent challenges in responding to suppression efforts by governments in Egypt, China and elsewhere. What the Tor members have learned in these recent incidents is that while governments are becoming more up front about their willingness to shut off Internet access altogether or censor content, users are also becoming more resourceful. Mathewson said that the group is working on methods for alleviating the problems that national-level restrictions cause for Tor users. One method involves moving to a modular transport method in order to get around some of the throttling that ISPs perform on encrypted traffic in order to make Tor usage more difficult. In a separate talk at LEET, Stevens LeBlond of INRIA in France presented research on methods for tracing Tor users back to their IP address. One of the attacks, which LeBlond and his co-authors titled 'Bad Apple,' used an exit node that the researchers controlled in order to trace the streams of data sent by users of BitTorrent over Tor back to their IP addresses."
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Attacking and Defending the Tor Network

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  • Re:Never 100% safe (Score:5, Informative)

    by alan_dershowitz (586542) on Tuesday March 29, 2011 @04:05PM (#35657748)

    The attack relies on the way Bittorrent is used and the fact that it uses UDP for contacting peers (which Tor doesn't route, causing only the tracker connection to be Torified) causing information leak; controlling an exit node to do a MitM); and the fact that Tor multiplexes multiple streams through the same node for performance reasons (meaning you can observe all the traffic that someone is going to through your exit node, once you've established who they are.)

    This attack won't work on you if:

    1. You are only using one app, in particular it won't work on you if all you're using is a browser and TorButton
    2. The same app is not sending data across both Tor and no-Tor
    3. The app in question can detect tampered-with data (SSL cert mismatch, etc.)
    4. As a precautionary measure, you are doing strict firewall egress filtering while using Tor.

    In short, if you are technically knowledgeable and careful, this attack doesn't apply to you. So, it's not the end of the road for Tor and anonymity, although it's a problem for "regular" people using Tor who can't be expected to keep track of all the ways their computer can unmask them.

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