Computer hackers from the Anonymous collective claimed responsibility Thursday for attacks on several high-profile Web sites in  revenge for the Department of Justice takedown of popular file-sharing Web site Megaupload.

The FBI and Justice Department coordinated on one of the largest criminal copyright infringement cases in U.S. history Thursday, when they announced they had shut down and charged its executives with racketeering, money laundering and conspiracy. In response to this, Anonymous hacktivists took to the Internet and claim to have brought down, and Web sites for the Department of Justice, Universal Music Group, the U.S. Copyright Office and more.

Anonymous may be using a distributed denial of service attack, or DDOS, where a flood of traffic is sent to a particular Web site to overwhelm servers and knock the site down. At the time of this post, the DOJ site is back up, but running very slowly, and reports across the Web say the sites have been coming in and out since the attack started.

All of this comes on the heels of a mass online protest Wednesday, when Wikipedia, Reddit, BoingBoing and other Web sites went dark in protest of the Stop Online Piracy Act. Despite an effort to say the Megaupload takedown was not related to this protest, federal authorities may have nevertheless courted the Anonymous retaliation with the maneuver. SOPA and its sister bill in the Senate, the Protect IP Act, are designed to go after copyright infringement online, and both bills are working their way through Congress.

Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., one of PIPA's sponsors, praised the FBI raids.

Today's action by the Department of Justice against the leaders of shows what law enforcement can do to protect American intellectual property that is stolen through domestic Web sites, Leahy said in a statement.

Tell us in the comments if you blacked out your Web site or Twitter feed to protest SOPA.