Notorious hacker group Anonymous has posted a defiant message to police and boasted of plundering sensitive data from NATO computers.
"We are not scared anymore," 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 the point, a message posted at a 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 arrested 16 people for cyber crimes on Tuesday, including 14 over an online attack on the PayPal website claimed by Anonymous. British police arrested one suspect and Dutch police four.
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.
Anonymous hackers called the PayPal attacks "Operation Avenge Assange," in reference to WikiLeaks founder Julian Assange, the indictment said, adding that the US raids were coordinated with police in Britain and the Netherlands.
In all, FBI agents made 35 raids across the United States as part of a probe into "coordinated cyber attacks against major companies and organisations," the FBI said, adding that to date more than 75 searches have been carried out.
Arrests show that police are gaining ground on Anonymous and serve as warning to sympathizers that may be considering joining the group, according to Luis Corrons of PandaLabs computer security firm in Spain.
"But Anonymous does not feel intimidated, and to show that they think they should strike harder," Corrons said.
"So, we are getting into a problematic spiral of violence."
Anonymous said its targets are governments that manipulate people with lies and fear, and corporations that lobby and ally themselves with such governments for profits.
"These governments and corporations are our enemy," the message at pastebin.com read.
"And we will continue to fight them, with all methods we have at our disposal, and that certainly includes breaking into their websites and exposing their lies."
Colombia's President Juan Manuel Santos on Wednesday tweeted that his Facebook page had been hacked by Anonymous, which took a swipe at the country's independence celebrations.
Anonymous left short phrases that are one of its calling cards, and a link to a video entitled "False Independence" on his personal page as Colombia marks the 201st year of its independence from Spain.
Anonymous also sabotaged Turkish sites last month to protest against internet censorship.
"The Anonymous bitchslap rings through your ears like hacktivism movements of the 90s," said the online message rebutting FBI comments condemning the group's attacks.
"We're back and we're not going anywhere," it continued. "Expect us."
Anonymous rose to infamy last year with cyber attacks in support of WikiLeaks.
The group was linked to attacks on Visa, Mastercard and PayPal, which blocked donations to the controversial anti-secrecy WikiLeaks after it published a quarter million US diplomatic cables stolen in a cyber attack.
"It seems that the only way the Anonymous group has to protest is by committing illegal acts," PandaLabs said this month in a security report that noted a slip from "hacktivism to stupidism."
"However, if the members of the group were smart enough, they would realise that their constant breaking of the law undermines the legitimacy of their protests," the report continued.