Online hacktivist group Anonymous did not release the cache of emails belonging to Rupert Murdoch on 22 July, but the group sprang a surprise by posting data it claims have been stolen from the database of NATO.

The group posted a message on Twitter, "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 message followed up by links to alleged NATO data.

NATO has said that it is aware of the alleged breach and has started a probe on the claims of the hackers.

Announcing the breach, Anonymous mocked at the security of NATO’s databases.

A message read: "Hi NATO. Yes we haz more of your delicious data.

You wonder where from? No hints, your turn."

The group also said, "You call it war; we laugh at your battleships."

This is the second time a hacker group has referred to ‘war’ while announcing a breach.

Another hacker group, Lulz Security (LulzSec) had first referred to the word after hacking the database of senate.gov, a government website in the US.

LulzSec had asked, "Is this an act of war, gentlemen?"

Last month, LulzSec and Anonymous had announced the "AntiSec" campaign against Internet regulation by governments across the world.

The two most prominent hacker groups in the Web world said that they will work together in their attacks against targets related to government such as banks. The groups had also urged people to steal and leak classified information.

LulzSec said in a statement, "Our Lulz Lizard battle fleet is now declaring immediate and unremitting war on the freedom-snatching moderators of 2011."

In its Web manifesto against governments, LulzSec had said the "Top priority is to steal and leak any classified government information, including email spools and documentation…Prime targets are banks and other high-ranking establishments. If they try to censor our progress, we will obliterate the censor with cannonfire anointed with lizard blood."

The group added, "DDoS is of course our least powerful and most abundant ammunition. Government hacking is taking place right now behind the scenes."

However, since then, there have been several coordinated crackdowns and arrests on alleged members of the hacker groups across the world.

Governments around the world are tightening their grip on cyber crime and hacking. The Pentagon has called cyber attacks as acts of war. The Obama administration is pressing Congress to approve a bill which will allow the present 10-years maximum punishment for hacking to be raised to 20 years. Japan has added new laws with stiffer punishments for hacking as well. New Zealand and Malaysia have also taken stern action against online piracy in recent days.

Two weeks ago, LulzSec has announced that the group is disbanding to escape government action.

Earlier this week, US authorities detained 14 people allegedly members of Anonymous. There were arrests in the UK and Netherlands as well.

However, this week, hackers announced their presence by breaching the website security of Rupert Murdoch owned The Sun.

In a move believed to be against corporate wrongdoing, they placed a fake page on the website claiming that Murdoch was dead.

The group also dared authorities to take action against the members of the hacker group.

LulzSec had challenged, "Arrest us. We dare you. We are the unstoppable hacking generation…."

Now the group has warned that it may release more data from NATO.

"In the next few days, wait for interesting data," the group said in a message.