Computer hackers working for the activism collective Anonymous announced today that NATO has been the victim of their latest Internet crime.

In a tweet today from the hacktivist group responsible for such high-profile infiltrations as ones perpetrated again Mastercard, Visa and PayPal in the past, Anonymous announced that, “Yes, we haz [sic] more of your delicious data.”

Anonymous doesn’t intend on disclosing all of what they’ve lifted from NATO servers, however — that, says the group, would be “irresponsible.” So far they have only released a single PDF file of a document headed with the message “NATO Restricted” dated to August of 2007. The group has hinted that some of the info will be leaked in the days to come.

The group notes that they have obtained roughly 1 GB of computer data.

One spokesperson for the North Atlantic Treaty Organization tells the Telegraph that it is investigating the claims. "We strongly condemn any leak of classified documents, which can potentially endanger the security of NATO allies, armed forces and citizens,” says another NATO spokesperson that would not be named by the AP.

While law enforcement officials and investigators worldwide are largely condemning an attack on such an established and powerful institution, Anonymous has fired back, taking a jab at the operations of associated governments. In a document released in conjunction with fellow hackers LulzSec today, Anonymous responds to a message from FBI Deputy Assistant Director Steve Chabinsky in which he calls Anonymous’ actions “unacceptable.”

“Now let us be clear here, Mr. Chabinsky, while we understand that you and your colleagues may find breaking into websites unacceptable, let us tell you what WE find unacceptable,” responds Anonymous.

The hackers add their own complaints against “the FBI and international law authorities” include “Governments lying to their citizens and inducing fear and terror to keep them in control by dismantling their freedom piece by piece” and “Corporations aiding and conspiring with said governments while taking advantage at the same time by collecting billions of funds for federal contracts we all know they can't fulfil.”

“We become bandits on the Internet because you have forced our hand,” write the hackers. “The Anonymous bitchslap rings through your ears like hacktivism movements of the 90s. We're back – and we're not going anywhere. Expect us.”

Anonymous offshoot LulzSec has previously attacked the computer servers of the CIA, Senate and SONY, among others. On Monday they hacked the website of News Corp’s The Sun and earlier today revealed that they would be releasing emails obtained from the servers of News of the World.