A cyberattack shut down a website for the NYPD captains union, targeting it with malware, union officials said.

Hackers from the group Anonymous, which supported the Occupy Wall Street movement and recently started an online war with ISIS, corrupted the website of the Captain Endowment Association on Friday.

“There are indications the attack on our website was orchestrated by a group identifying themselves as “Anonymous” who have a history of targeting police websites across the country,” wrote the union’s president Roy Richter, in a letter to members.

The group hacked into the California Statewide Law Enforcement Association’s website in 2012– and released it’s members’ addresses, as well as credit card information.

Richter wrote that the captain’s association does not store any personal information about union members on the website, and that no “confidential information has been compromised.”

The letter also noted that the association was adding new security protections to the website, and that the union considered the attack more an irritation than a threat.