Saboteurs stole passwords and sensitive information on tipsters while hacking into the Web sites of several law enforcement agencies worldwide in attacks attributed to the collective known as Anonymous.
Breaches were reported this week in Greece, as well as Boston, Syracuse, New York, Salt Lake City in the US.
Hackers gained access to the Salt Lake City Police Department Web site that gathers citizen complaints about drug and other crimes, including telephone numbers, addresses and other personal data of informants, police said.
The Web site remained down on Friday as police worked to make it more secure.
Anonymous is a collection of Internet enthusiasts, pranksters and activists whose targets have included financial institutions such as Visa and MasterCard, the Church of Scientology and law enforcement agencies.
Following a spate of arrests across the world, the group and its various offshoots have focused their attention on law enforcement agencies in general and the FBI in particular.
The group also claimed responsibility for hacking the Web site of a Virginia law firm that represented a US Marine involved in the deaths of civilians in Iraq in 2005.
Anonymous also published a recording on the Internet on Friday of a telephone call between the FBI and Scotland Yard, gloating in a Twitter message: “The FBI might be curious how we’re able to continuously read their internal comms for some time now.”
FBI spokeswoman Jenny Shearer said in an e-mail that the agency was aware of the incidents, and an investigation was ongoing.
In Greece, the Greek Ministry of Justice took down its site on Friday after a video by activists claiming to be Greek and Cypriot members of Anonymous was displayed for at least two hours.
In Boston, a message posted on the police Web site before it was taken down on Friday said: “Anonymous hacks Boston Police Web site in retaliation for police brutality at OWS,” an apparent reference to the Occupy Wall Street movement.
The message also said: “There is plenty more mayhem to deliver.”
A police spokesman would not confirm whether Anonymous was responsible.
Another message on the department’s Web site said a hack several months ago unearthed hundreds of passwords that were released in retaliation for what was called brutality against Occupy Boston protesters.
In October, Boston police acknowledged that various Web sites used by members of the police department — including the Web site belonging to the police patrolmen’s association — had been hacked and possibly compromised. The department said it asked all police personnel to change their passwords on its network.
The Occupy movement in Boston set up camp in the city’s financial district for two months this fall. The first hack came about 10 days after Boston police arrested 141 Occupy demonstrators on Oct. 11.