In a defiant statement addressed largely at FBI director Steve Chabinsky, members of the Anonymous and LulzSec hacktivist groups vowed to continue with their hacking campaigns and dared law enforcement to try and stop them.
The statement comes just two days after the FBI arrested 14 alleged members of Anonymous in connection with a series of distributed denial of service (DDoS) attacks against PayPal last year.
ANALYSIS: Who are all these hacker groups?
The immediate provocation appears to have been some comments made by Chabinsky in a NPR report following the recent arrests.
In it, Chabinsky is quoted as saying that chaos on the Internet is unacceptable. "[Even if] hackers can be believed to have social causes, it's entirely unacceptable to break into websites and commit unlawful acts."
In their response, posted on Pastebin.com , Anonymous and LulzSec members claimed their hactivist campaigns were motivated by a desire to expose what they described as lying governments, corrupt corporations and powerful lobbyists.
"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," the letter said.
"We are not scared any more. Your threats to arrest us are meaningless to us as you cannot arrest an idea," the groups claimed. The two groups claimed they were acting like bandits only because they were forced to. "The Anonymous bitchslap rings through your ears like hacktivism movements of the 90s. We're back -- and we're not going anywhere."
Given the highly decentralized and loosely organized nature of the two groups it's hard to say how much of the content in the letter is bluster, how much is real or even how much it represents the true sentiment among members.
Certainly both Anonymous and LulzSec have demonstrated their ability to strike at what appears to be pretty much at will and pretty much against any target.
Just today for instance, Anonymous released a 36-page restricted document that is claimed to have obtained by breaking into a Web server at North Atlantic Treaty Organization (NATO) .
In a Twitter message, the group said that it has 1GB of material from NATO which it would not release because it would be irresponsible.
Over the last week, both groups have claimed credit for breaking into Rupert Murdoch's media sites. In one attack LulzSec compromised DNS servers at News International so that visitors to the group's Sun tabloid site were redirected to a fake story proclaiming Murdoch's death.
And in recent weeks and months both Anonymous and LulzSec have claimed responsibility for breaks-in at military contractor Booz Allen Hamilton, Sony and several other high-profile organizations.
The attacks have been mostly designed to embarrass and to provoke rather than to create any real damage. In most instances, the groups have cited some political or social cause for their attacks.
Recently for instance, when Anonymous attacked police union sites in Arizona , it claimed it was doing so because of the state's tough immigration laws.
However, law enforcement has made some important gains as well. Last weeks raids for instance, netted a total of 14 individuals who are allegedly members of Anonymous. Several arrests have been made overseas as well. Last month U.K police arrested Ryan Cleary, a 19-year old who is believed to be connected to both LulzSec and Anonymous.
Computers seized from last week's arrests and from Cleary's arrests are likely to lead authorities to more people connected with the two groups.
Whether such arrests will dampen their enthusiasm or only spur more attacks remains to be seen.
Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan or subscribe to Jaikumar's RSS feed . His e-mail address is email@example.com .
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This story, "Anonymous, LulzSec vow to hack on" was originally published by Computerworld.