QuoteThe first attack is on people who configure their Bittorrent application to proxy their tracker traffic through Tor. These people are hoping to keep their IP address secret from somebody looking over the list of peers at the tracker. The problem is that several popular Bittorrent clients (the authors call out uTorrent in particular, and I think Vuze does it too) just ignore their socks proxy setting in this case. Choosing to ignore the proxy setting is understandable, since modern tracker designs use the UDP protocol for communication, and socks proxies such as Tor only support the TCP protocol -- so the developers of these applications had a choice between "make it work even when the user sets a proxy that can't be used" and "make it mysteriously fail and frustrate the user". The result is that the Bittorrent applications made a different security decision than some of their users expected, and now it's biting the users.The attack is actually worse than that: apparently in some cases uTorrent, BitSpirit, and libTorrent simply write your IP address directly into the information they send to the tracker and/or to other peers. Tor is doing its job: Tor is _anonymously_ sending your IP address to the tracker or peer. Nobody knows where you're sending your IP address from. But that probably isn't what you wanted your Bittorrent client to send.QuoteThat was the first attack. The second attack builds on the first one to go after Bittorrent users that proxy the rest of their Bittorrent traffic over Tor also: it aims to let an attacking peer (as opposed to tracker) identify you. It turns out that the Bittorrent protocol, at least as implemented by these popular Bittorrent applications, picks a random port to listen on, and it tells that random port to the tracker as well as to each peer it interacts with. Because of the first attack above, the tracker learns both your real IP address and also the random port your client chose. So if your uTorrent client picks 50344 as its port, and then anonymously (via Tor) talks to some other peer, that other peer can go to the tracker, look for everybody who published to the tracker listing port 50344 (with high probability there's only one), and voila, the other peer learns your real IP address. - from https://blog.torproject.org/blog/bittorrent-over-tor-isnt-good-ideaThey describe a third attack that involves analyzing traffic patterns at exit nodes, which doesn't apply in this case of course. I don't really understand how Tor circuit selection is made and how the possible options are tracked and reported to clients well enough to know if the above applies to directory mirrors in the Tor network in any way... don't those have to be reachable by their IP and kept "tracked" somewhere though, basically like a tracker?If everyone was semi-server, semi-client, then wouldn't everyone have to have a hidden service with 2 guards? Which would mean the Tor network would have to provide 2N guards for N site browsers, wouldn't it? That just doesn't seem at all feasible... ... I can't think straight; this is silly. Why am I even talking about this; I'd be hard pressed to tie my shoes properly right now. That's it, I hit my wall -- time to crash and come back when I'm not a basket case that's been awake too many days...