Notorious hacker group Anonymous has posted a defiant message to police and boasted of plundering sensitive data from NATO computers.

"We are not scared any more," read an online message that purported to be a response by Anonymous and splinter group Lulz Security.

"Your threats to arrest us are meaningless to us as you cannot arrest an idea... there is nothing - absolutely nothing - you can possibly do to make us stop."

As if to underscore its point, a message posted at Twitter account by AnonymousIRC claimed to have looted about a gigabyte of NATO data that even the rebel hacker group deemed too sensitive to release.

"Yes, we haz (sic) more of your delicious data," the Twitter post read. "You call it war; we laugh at your battleships."

US authorities on Tuesday arrested 16 people for cyber crimes including 14 over an online attack on the PayPal website claimed by Anonymous.

The US indictment against the 14 hackers alleges the denial of service (DDoS) attacks on PayPal were "retribution" because the site terminated a donation account for the whistle-blowing group WikiLeaks.

AFP