[Zirro]

I would assume it's enough for them to join a swarm to locate other peers. There are probably automated tools which can do this very quickly, just like I can see the IPs of fellow peers, both seeders and leechers in my torrentclient.

Both of your statements are true, though.

[guard-of-terra]

Oww. I didn't think of that.

[drostie]

You can see a prototype of an open system for this sort of thing here: http://www.youhavedownloaded.com/ . (Actually, that site is pretty interesting to visit if you're on a friend's WiFi or at an airport or internet cafe -- I just found out that, from this WiFi point, someone downloaded The Lion King in December 2011.)

But yeah. Pretty much any tracker is constantly disclosing peers; that's how BitTorrent works. It is considered important for a tracker to introduce fake IP addresses into these lists, so that simply being on the list is not enough to prove that someone was actually downloading a given bit of content, and there have now been research groups which have gotten takedown notices delivered to printers and so forth, so that if you're not confirmed to be seeding content it's hard to confirm that you're breaking the law.

It is also considered best practice with BitTorrent to use an IP blocklist with your client, but those are probably not too hard for a dedicated attacker to get around -- if you share illegal material and use an IP blocklist, you are basically saying "I will hope that you pick the low-lying fruit first, before you pick me."

[Zirro]

The best thing to do today if you want to be on the safe side is to use a VPN-service which doesn't keep logs. It's likely only a question of time before the anti-piracy organizations start going after them instead, though. Blocklists are, as you state, not very effective and often tend to contain false positives which gives you fewer peers.

[guard-of-terra]

This prototype always tells me they have no records on me :-/