Hacktivist group Anonymous has hit the United States Telecom Association and TechAmerica with distributed denial-of-service attacks, apparently for the trade groups' support of a controversial cybersecurity bill in the U.S. Congress.

Anonymous posted a YouTube video showing USTelecom's site down Sunday, and the site was down for about 24 hours, according to a USTelecom spokesman. The trade group discovered that the site was down at about 6 a.m. Monday, he said.

TechAmerica's site was still down at 2 p.m. ET Monday after being hit on Sunday, a spokeswoman there said.

Anonymous on Friday released a YouTube video threatening supporters of the Cyber Intelligence Sharing and Protection Act, a bill focused on encouraging U.S. government agencies and private businesses to trade information about cyberattacks.

The bill would harm the Internet, the video said. "We will unleash the worst pain on those who threaten our existence," the video added.

Supporters of the bill, CISPA for short, are "sworn enemies" of Anonymous, the video said.

Some digital rights groups, including the Center for Democracy and Technology and the Electronic Frontier Foundation, have raised privacy and civil liberties concerns about CISPA.

The bill would allow private companies to share broad information about cyberthreats with government agencies, with no requirement to strip out personal information, CDT said in a press briefing last week. CISPA, sponsored by Representative Mike Rogers, a Michigan Republican, would allow U.S. agencies to use the information shared by private companies for other national security and law enforcement purposes, in addition to cybersecurity, CDT said.

USTelecom respects the right of Anonymous to engage in "lawful political advocacy," said Walter McCormick Jr., USTelecom's president and CEO.

"But by launching a cyberattack in an effort to coerce, intimidate and stifle speech, members of Anonymous are acting contrary to the very freedoms and Internet norms that they espouse," McCormick said in a statement. "Ironically, by their actions Anonymous hacktivists underscore the importance of speedy action on the bipartisan ... legislation to ensure that the Internet remains an open and safe forum for all."

CISPA is an "important tool" for combating cyberattacks, said Shawn Osborne, TechAmerica's president and CEO.

"These types of strong-arm tactics have no place in the critical discussions our country needs to be having about our cybersecurity, they just underscore the importance of them," he said in a statement. "CISPA is designed to defend against cyberattacks and keep the internet free and open."

Other trade groups that have voiced support for the Rogers bill said either that they had not been attacked or declined to comment.

Trade groups and companies that have voiced support for the Rogers bill include AT&T, CTIA, Facebook, IBM, Intel, Microsoft, and the National Cable and Telecommunications Association.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is grant_gross@idg.com.