In response to a bill now before Congress, which opponents say would dramatically erode internet freedom, the free and fair use of copyrighted material and online privacy, hacker groups have begun to publicly threaten to launch attacks on US government workers and websites.

The US House Judiciary Committee debated for a second day on Friday the Stop Online Piracy Act (SOPA), a bill that would bestow the US Department of Justice and individual copyright holders with unprecedented powers to shut down websites and crack down on users for what they deem to be violations of copyrights.

The vote was postponed after day two of the debate after a wayward tweet derailed talks on Thursday. Rep. Steve King (R – Iowa) tweeted that Rep. Sheila Jackson Lee (D – TX) was “boring.” The hearing then grinded to a halt after Jackson Lee took issue with the offensive comment. The hearing fell behind schedule and the vote was delayed until Dec. 21.

The delay will give the bill’s detractors more time to organize its calls for the bill to be dropped. The bill as it now stands appears to have enough votes to pass the House of Representatives and move on to the Senate.

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But opponents — including Google, Yahoo, Facebook, Twitter, eBay, Mozilla, the Brookings Institute, Reporters Without Borders, the ACLU, and Human Rights Watch — argue that SOPA would cause “an explosion of innovation-killing lawsuits and litigations,” a line that echoes the opinions of many Congressional democrats.

Abandoning letter-writing campaigns and other traditional lobbying efforts, some prominent online hacker groups are now threatening to resort to more direct action.

Anonymous, a hacker organization that made headlines earlier this year by shutting down government websites during the uprisings in Tunisia and Egypt, said Friday it was preparing to launch what it called “Operation Blackout,” and rallied Americans to participate in nationwide protests in an effort to stop the legislation from passing.

“The United States government shall see that we are truly legion and we shall come together as one force opposing this attempt to censor the internet once again,” Anonymous said in a video posted online.

Although denying that their announcement was a call to arms for would-be hackers, Anonymous and its allies said that what it deems to be “acts of oppression” would be met with retaliation.

“We, Anonymous, know that this is a hidden campaign to destroy the ability of people across the world to connect and share their experiences with one another. To the American Congress: If you pass this bill, you will pay for it,” the group said.

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4chan, an online forum that is widely considered the darkest, most murky corner of the internet, and which was the birthplace of the Anonymous hacker collective, is awash with calls to arms. In between postings of pornographic images and internet memes, users watched the live internet stream of the SOPA debate among the house judiciary committee, discussing possible means for retaliation should the bill make it to the floor of the US House of Representatives for a vote.

For Anonymous and their hacker brothers-in-arms LulzSec, attacking US government websites is nothing new. The two groups, and a few others, turned last summer into a hack-fest of unseen magnitudes, attacking numerous US government websites, including those belonging to the CIA, the FBI, and the Senate, all in retaliation for the arrest of hackers in the US and the UK. The group also attacked corporate sites belonging to companies like PayPal and Sony for their role in limiting the ability of Wikileaks to receive donations.

But these hacks were not intended to compromise national security or steal credit card information, the hackers said. Anonymous’ hack of choice is the distributed denial of service attack (DDoS), which forces websites to shut down for a finite period of time, embarrassing the organization and, in some cases, causing it to lose revenue. Occasionally, the hackers have also published personal information belonging to employees.

Lamar Smith (R-Texas), the representative that introduced the SOPA bill, has had his personal information released on both pastebin.com (a popular text hosting website used by LulzSec and Anonymous) and 4chan, including his home and work telephone numbers and addresses, as well as other information found on his tax documents.

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Other congressmen and judiciary committee staffers have had their personal phone numbers and home addresses made public as well.

While many 4chan users, operating under the Anonymous banner, demanded that proponents of the bill be harassed using the newly public information, others warned such actions would only serve to further the argument that SOPA is necessary to protect not only copyrights but also personal privacy.

Nevertheless, in the extra time it now has before the bill goes to a vote, Anonymous and other hacker collectives, which view themselves as being under direct, existential threat, hope to rally like-minded individuals to help stop the legislation, encouraging passive internet users to join what could become Anonymous’ largest cyber war yet.