Anonymous is now planning to attack Facebook on January 28, according to a warning video.
The video which warns of the attack was added to YouTube on January 23.
"An online war has begun between Anonymous, the people and the government of the US," the video says.
"While SOPA and PIPA may be postponed from Congress, this doesn't guarantee that our Internet rights will be upheld."
Anonymous had earlier hacked the U.S. Department of Justice's website and a host of other sites after the US authorities brought down the file-sharing site Megaupload on charges of piracy.
The video appeals to Americans to join the attack by downloading Low Orbit Ion Cannon (LOIC). LOIC is the same tool that was used to damage the Department of Justice, according to a Mashable report.
Websites can be crashed using LOIC which sends thousands of information nodules to their servers, Mashable reports.
The video carries instructions about downloading and running the program as well as timing of the attack. But no time zone is mentioned.
"Would you like to become part of the greatest Internet protests and first official cyber war?," the video asks. "Operation Global Blackout is ongoing and everyone can be a part of it."
Facebook is one of biggest social network sites with millions of users. In the video, Anonymous acknowledges that it would be difficult to attack Facebook, which operates through several servers spread across the world.
Facebook did speak up against anti-piracy bills SOPA and PIPA, so its questionable why Anonymous would like to damage the site.
Facebook, according to a CNET report is ready for any attack.