WASHINGTON - The US Senate's website was hacked over the weekend, leading to a review of all of its websites, in the latest embarrassing breach of security to hit a major US-based institution.

The loosely organized hacker group Lulz Security broke into a public portion of the Senate website but did not reach behind a firewall into a more sensitive portion of the network, Martina Bradford, the deputy Senate sergeant at arms, said on Monday.

Despite the breach, the Sergeant at Arms Office, which provides security for the Senate, said that the breach had not compromised any individual senator's information.

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Lulz announced the hack on Monday.

"We were responding to their allegations. Basically what we're saying that the server they got into is for public access and is in the public side," said Bradford.

Lulz Security, who have hacked into Sony's website and the US Public Broadcasting System, posted online a list of files that appear not to be sensitive but indicate the hackers had been into the Senate's computer network.

"We don't like the US government very much," Lulz Security said at the top of their release. "This is a small, just-for-kicks release of some internal data from Senate.gov - is this an act of war, gentlemen? Problem?"

The comment refers to reports that the US military had decided that it could respond to cyber attacks from foreign countries with traditional military force.

Senate staffers were alerted about the breach late Monday.

"Although this intrusion is inconvenient, it does not compromise the security of the Senate's network, its members or staff," Bradford said in a statement. "Specifically, there is no individual user account information on the server supporting senate.gov that could have been compromised."

"The hackers may have done the equivalent of burglarizing the Senate and bragging because they managed to steal a bunch of souvenirs from the gift shop," said Stewart Baker, a former cyber official at the Department of Homeland Security. He is now with the law firm Steptoe and Johnson.