HOW TO: Protect your P2P privacy
Without getting into the quagmire that is the debate over P2P, fronted on one side by sane 
technologically able people and on the other by a dying breed of middlemen with an outdated business model (ok, so I dipped a toe into the marsh), the use of the technology aptly includes both legitimate claims of copyright infringement and illegitimate claims that this is all the technology is good for. In fact, P2P is rapidly becoming the de-facto mechanism distribution of all sorts of content on the Internet.
But I digress — if you use P2P software, and this can include programs that use it for distribution (which may not be immediately apparent to you), whether you like it or not you’re putting your IP address and machine on the global invitation list. It doesn’t matter that you’ve got a firewall — for while it does its job at the protocol and port level, it can’t protect you from the applications you run that openly share information about you or your machine.
Such as P2P software. HOW TO: Protect your P2P privacy | APC Magazine