Members of the Anonymous hacking collective said they broke into the networks of Mantech International and stole internal documents belonging to the US government contractor.

As proof, the members posted a 390 MB download that appeared to contain reports related to NATO, the US Army and personnel files. A note that accompanied the Bittorrent file said the hack was intended to defy the FBI, which last week charged 14 people of participating in an Anonymous-led web attack in December that created service disruptions for some PayPal customers.

“Dear Government and Law Enforcement, we are repeating this message as we have the suspicion you still do not take us seriously,” their 715-word screed, which was titled “FUCK FBI FRIDAY,” read in part. “We are not scared anymore and your threats to arrest us are meaningless. We will continue to demonstrate how you fail at about every aspect of cybersecurity while burning hundreds of millions of dollars that you do not even have.”

The leaked documents appeared to have little or no connection to the FBI, although press releases appeared to show that the FBI has outsourced some of its IT security to Mantech. The Washington, DC-based firm has also signed contracts to provide services to the departments of Defense, State, Homeland Security, Energy and Justice.

A statement posted to Mantech's homepage said the company “takes seriously recent reports of a cyber threat, and we responsibly and actively address all sources of information about threats to our information and assets and those of our customers.” It neither confirmed nor denied the Anonymous claims Mantech was compromised “utterly and throughly” [sic].

The document dump comes after Anonymous and its Lulz Security offshoot have claimed responsibility for brazen attacks on the US CIA, the US Senate, and various Arizona law enforcement agencies, among many others.

The document dump came a few days after UK police claimed they arrested a central LulzSec figure. On Friday, investigators with Scotland Yard received an extension giving them three more days to detain the 18-year-old they say was the figure known as Topiary. The extension cast doubt on speculation the unidentified man was a fall guy who was framed to take the heat off the real culprit. ®