Online activists angered over antipiracy legislation in Congress as well as today's indictment of operators of popular file-hosting site MegaUpload attacked the sites of the U.S. Department of Justice, the FBI, Universal Music, and the Motion Picture Association of America, shutting them down at least temporarily, and were targeting many others.

"The Largest Attack Ever by Anonymous - 5,635 People Confirmed Using #LOIC Bring Down Sites!" the AnonDaily Twitter account read, referring to the Low Orbit Ion Cannon (LOIC) tool Anonymous supporters use to launch distributed denial-of-service (DDOS) attacks on sites.

Apparently Anonymous tried a new tactic in its attack campaign -- disseminating a Pastebin link that when clicked automatically launched a Web-based version of LOIC. People clicking on the link, thinking they were going to be getting new information from Anonymous about the attack, instead were having their computers take part in the attack. The page appeared to be aimed at the MPAA when this reporter saw it before quickly closing it.

The attacks were affecting Internet traffic patterns overall, according to a real-time Web monitoring site operated by content delivery company Akamai. The site had registered 218 attacks in the last 24 hours and reported that attack-related traffic was up 24 percent over normal, while general network traffic was up 13 percent.

IRC chats show supporters of the Anonymous online activist collective claiming victory over shutting down the Justice Department site and talking about other U.S. government sites to target, including the Recording Industry Association of America (RIAA), the White House, the FBI, BMI.com, Copyright.com, Viacom, Anti-piracy.be/nl, Vivendi.fr, Hadopi.fr, and ChrisDodd.com, the site for the former U.S. senator who now heads up the MPAA. Some of the targeted sites were intermittently down, like the FBI, while others were accessible but opening very slowly. (A list of known targets is here.)

The activists are angry about two proposed antipiracy bills backed by the music and movie industries, SOPA and PIPA, that critics say would give authorities broad power to shut down Web sites for the mere accusation that they had pirated content on them.

Screenshot by CNET

"Seems like some friendly ships are launching torpedos justice.gov as we speak. The site seems down to us! (via @AnonOpsSweden)," Twitter accounts associated with the Anonymous online activist group posted today.

"RIAA.ORG DOWN! The Largest On Scale Attack EVER by #Anonymous 10 sites in 20 minutes," the Anon Daily Twitter account read. "#OPMegaUpload is in Full Effect. Justice.gov DOWN - MPAA.org DOWN - UniversalMusic.com DOWN - MASS DDOS ATTACK!"

Shortly before the outages, seven people were named in an indictment and four were taken into custody on online piracy charges. One of those arrested was Kim Dotcom, aka Kim Schmitz, the founder of Megaupload, an Internet locker service.

A Justice Department spokesperson provided this comment: "The Department of Justice Web server hosting Justice.gov is currently experiencing a significant increase in activity, resulting in a degradation in service. The department is working to ensure the Web site is available while we investigate the origins of this activity, which is being treated as a malicious act until we can fully identify the root cause of the disruption.

Universal Music had no comment.

The attacks were designed to forcibly shut down sites in protest, but a number of big Web sites and tech companies, including Google and Wikipedia, expressed their anti-SOPA sentiments yesterday by blacking out or otherwise changing their sites.

The widespread opposition to the the controversial antipiracy measures appeared to be having an effect on lawmakers, including senators who are scheduled to vote on their version--dubbed Protect IP Act or PIPA--next Tuesday. Several senators said they were withdrawing their names as co-sponsors or voting against the measure and some representatives also expressed wavering support yesterday.

Akamai

Updated January 20 at 7:35 a.m. PT with Anonymous using automatic LOIC tool for attacks and January 19 at 5:07 p.m. PT with Akamai reporting Web attack statistics and 4:51 p.m. PT with FBI site downed and DOJ comment, 3:53 p.m. PT with more details and background, 3:19 p.m. PT with more targets and details, and 2:45 p.m. PT with Universal Music and MPAA down and more background and details.