As a part of its ongoing AntiSec campaign Anonymous hackers have reportedly breached NATO's cyber security making-off with one gigabyte of stolen data.

Like its previous attacks the hack was reported on the group's Twitter page. Anonymous has since released two PDFs containing a portion of the data stolen, linking to them via two tweets:

"We think, actually we may not release emails from The Sun, simply because it may compromise the court case. But..

"Here is the next NATO Restricted PDF: | Outsourcing CIS in Kosovo (2008) | Enjyoing the war yet, NATO? #AntiSec"

The group has since clarified that it will not be releasing a significant portion of the data due to its sensitive nature:

"Yes, #NATO was breached. And we have lots of restricted material. With some simple injection. In the next days, wait for interesting data :)

"We are sitting on about one Gigabyte of data from NATO now, most of which we cannot publish as it would be irresponsible. But Oh NATO...."

The first document released by the group came from 2007. The allegeded NATO document is funding request on communication systems for the Joint Communications Control Centre, which supported ISAF forces in Afganistan.

The second document, dated a year later in 2008, is proposal document outlining plans to outsource Nato forces communications systems in Kosovo.

The attack has been credited as a part of the group's ongoing AntiSec campaign. To date the group has targeted numerous governments and agencies it views as corrupt, or overtly attempting to censor or moderate the internet.

The group has had previous misgivings about NATO after the military organisation listed Anonymous as a terrorist group.