Infamous hacking enclave Anonymous continued its quest for retribution Tuesday, claiming responsibility for shutting down OnGuardOnline.com, a Website managed by the U.S. Federal Trade Commission (FTC).

The FTC could not be immediately reached for comment.

The shutdown extended to five days Anonymous's retaliation against the government's termination of file-sharing Website MegaUpload.com and the arrest of founder Kim Schmitz, widely known as Kim Dotcom.

Sen. Chuck Grassley (R-Iowa) experienced the Anonymous attacks firsthand on Monday when the hacktivist group gained access to his Twitter account.

One message from the pirated account read: “Dear Iowans, vote against ACTA, SOPA, and PIPA, because this man, Chuck Grassley, wants YOUR internet censored and all that BS.”

“Senator Grassley’s staff noticed the hacking after the first false Tweet was posted,” communications director Beth Levine said Tuesday. “The office immediately called Twitter to obtain access to the account so the password could be changed.”

Sen. Grassley, who recently renounced his support of the Senate’s anti-piracy legislation Protect IP Act (PIPA), has since regained control of the account. SOPA, the Stop Online Privacy Act, is the House counterpart of PIPA. Both are widely supported by the entertainment industry. ACTA is the Anti-Counterfeiting Trade Agreement, a proposed agreement between the U.S. and a number of other countries.

In a YouTube video released by Anonymous on Monday, a deep, robotic voice warned: “While it is true that Facebook has at least 60,000 servers, it is possible to bring you down.” The group went back on its threat Tuesday.

According to a U.S. Department of Justice press release, German-born Dotcom is responsible for generating more than $175 million in illegal profits and causing more than half a billion dollars in harm to copyright owners.

“We are aware of the situation and will continue to perform our investigations,” Federal Bureau of Investigation spokeswoman Adrienne Senatore said Tuesday.

The claims against Dotcom include conspiring to commit copyright infringement, conspiring to commit money laundering and criminal copyright infringement, the Department of Justice stated in the release.

In a hearing Monday in New Zealand, a judge delayed the decision to release Dotcom on bail.

The Internet collective known for protesting online censorship also struck over the weekend, and allegedly took down several sites in the United States including UniversalMusic.com. The company could not be reached for comment.
 
Anonymous also took credit for shutting down CBS for about 20 minutes on Sunday. The group tweeted the following message Sunday under the handle, YourAnonNews: “Anonymous Deletes CBS, Universal Sites; is Xbox Live Next?”

Sources within CBS said the site was undergoing routine software updates on Sunday, and that the shutdown didn’t have anything to do with hackers.