The FBI is in possession of log data that contains the IP addresses of participants in last months series of distributed denial of service (DDoS) attacks orchestrated by the pro-WikiLeaks ensemble known as Anonymous.
Anonymous and members of the hacker social network 4chan have been engaging in multiple DDoS attacks against the websites of organizations and individuals they deem to be stifling WikiLeaks efforts to distribute classified materials and raise funds.
The attacks were largely possible due to the notion that the crowd-sourced participants could remain unidentified (see Anonymous Movement is Fueled by Cowardice for more on this).
A DDoS tool dubbed the Low Orbit Ion Cannon (LOIC) was distributed widely via downloads from multiple forums and websites.
What the so-called "leaders" of the Anonymous minions failed to relay to the participants in the DDoS attacks is that the LOIC tool would send their IP addresses along with every packet during the attack. The FBI will use the IP addresses to identify those who participated in the attack.
What can they expect now that their supposed anonymity has been compromised?
Law enforcement will probably concentrate on those suspected of organizing the attacks, at first. They are likely to conduct raids and seize digital media like computers, MP3 players, cell phones and more.