Ransomware gang leak US capital cops data

The police department in the US capital has suffered a massive leak of internal information after refusing to meet the blackmail demands of a Russian-speaking ransomware syndicate.

Experts say it is the worst known ransomware attack ever to hit a US police department.

The gang, known as the Babuk group, released thousands of the Metropolitan Police Department's sensitive documents on the dark web on Thursday.

A review by the Associated Press found hundreds of police officer disciplinary files and intelligence reports that include feeds from other agencies, including the FBI and Secret Service.

Ransomware attacks have reached epidemic levels as foreign criminal gangs paralyse computer networks at state and local governments, police departments, hospitals and private companies.

They demand large payments to decrypt stolen data or to prevent it from being leaked online.

Brett Callow, a threat analyst and ransomware expert at the security firm Emsisoft, said the police leak ranks as "possibly the most significant ransomware incident to date" because of the risks it presents for officers and civilians.

Some of the documents include security information from other law enforcement agencies related to US President Joe Biden's inauguration, including a reference to a "source embedded" with a militia group.

One document details the steps the FBI has taken in its investigation of two pipe bombs left at the headquarters of the Democratic National Committee and the Republican National Committee before the riots at the US Capitol on January 6.

That includes "big data pulls" of mobile phone towers and plans to "analyse purchases" of Nike shoes worn by a person of interest, the document said.

The newly released files include details of disciplinary proceedings of hundreds of officers dating back to 2004.

The files often contain sensitive and embarrassing private details.

"This is going to send a shock through the law enforcement community throughout the country," said Ted Williams, a former officer at the department who is now a lawyer.

The Babuk group indicated this week that it wanted $US4 million ($A5.2 million) not to release the files but was only offered $US100,000.

The department has not said whether it made the offer.