they use spider programs to scour the Internet and identify people who have files that "belong" to their customers, such as the RIAA -- this includes the files of those who use file sharing / P2P utilities.
It has been argued by BayTSP that they "only probe the ports on your computer that you have made public"... but this brings up an interesting argument, as this kind of probing appears to be illegal in certain localities. Also, their argument also seems to support warchalking -- the use of symbols to indicate the availability of wireless networks -- as both warchalking and port probing garner information through similar means. They can't have it both ways, can they?!
One way that this kind of probing can be prevented is for ISPs to block the IP addrs/ranges that are used for these spybots. For those who are interested in blocking these IP addresses/ranges, there is a list of them here. Like other web hosts and ISPs, LiveJournal should consider blocking these spybots as soon as possible.
Ultimately, what is needed is the establishment of a centralized list of IP addrs/ranges that known to be used by these spybots, and the creation of a grassroots effort to put pressure on ISPs so that they block these spybots, ideally giving credit to those ISPs and web hosts who are willing to put the privacy of their users first. Arguably, these businesses would be doing themselves a favor by blocking these spybots, as it would result in fewer copyright violation complaints, requests for personal violation, and takedown requests. Most importantly, it would throw a monkey wrench into future enforcement of the DMCA -- customers who want privacy would migrate to services that are willing to respect their privacy.
I'm putting out some feelers to see if something of the sort can be done -- blocking ports and IP addresses is a regrettable thing to have to do, but there is no law I know of that says that we, as a society, must tolerate those who would attempt to spy on us. We should have the right to lock our doors and keep them shut, both at home and online.