The CIA said Wednesday it was investigating reports that its public website had been targeted by hackers.
A group that calls itself Lulz Security has in the past few days claimed credit for a spate of cyber attacks on a number of high-profile targets, including the website of the US Senate.
"We are looking into reports the service is down," a CIA spokesman told FOX News Channel.
AFP reported that the US spy agency's www.cia.gov website stopped responding, while attempts by NewsCore to log on met with mixed success.
Lulz has stepped into the spotlight during an unrelenting wave of cyber attacks with apparent motivations ranging from spying and profit to glory and activism, AFP reported -- adding that the group brazenly ramped up its antics Wednesday.
US payroll-handling firm Automatic Data Processing on Wednesday joined a growing list of victims that has included Sony, the International Monetary Fund and Citibank. Lulz hackers have also claimed in recent weeks to have cracked into Nintendo, the US Senate, the Public Broadcasting System news organization and an Infragard company that works with the FBI.
The group is flaunting its notoriety with a telephone hotline for people to call and suggest targets for cyber attacks.
It is believed to have formed from hacker group Anonymous, which gained notoriety with cyber attacks in support of controversial website WikiLeaks, according to AFP.
"It's becoming a big problem, because at the end of the day these guys are doing whatever they want," said Panda computer security labs technical director Luis Corrons. "This is showing us that we have a long way to go to protect our systems and our information."
Unlike cyber criminals who amass armies of "zombie" computers by stealthily infecting machines with viruses, people volunteered to install software in support of Anonymous campaigns, according to Corrons.
"Anonymous has been out there for years," Corrons said, noting the group had launched attacks on music or movie firms taking people to task for pirated songs or films.
"When the WikiLeaks case came, they reacted fast and gained a lot of popularity," he said.