The website attacks launched by supporters of WikiLeaks show 21st-century cyber warfare evolving into a more amateur and anarchic affair than many predicted.

While most countries have plowed much more attention and resources into cyber security in recent years, most of the debate has focused on the threat from militant groups such as al Qaeda or mainstream state on state conflict.

But attempts to silence WikiLeaks after the leaking of some 250,000 classified State Department cables seem to have produced something rather different -- something of a popular rebellion amongst hundreds or thousands of tech-savvy activists.

The first serious infowar is now engaged, former Grateful Dead lyricist, founder of the Electronic Frontier Foundation John Perry Barlow told his followers on Twitter last week. The field of battle is WikiLeaks. You are the troops.

Some of the more militant elements on the Internet clearly took him at his word. A group calling itself Anonymous put the quote at the top of a webpage entitled Operation Avenge Assange, referring to WikiLeaks founder Julian Assange.

Online collective Anonymous appears to be using social networking site Twitter to coordinate attacks on websites belonging to entities it views as trying to silence WikiLeaks.

Targets have included MasterCard, Visa and a Swiss bank. All blocked payments to Wikileaks on apparent U.S. pressure.

Swedish prosecutors behind Assange's arrest in London for extradition and questioning over sex charges were also hit. Some Wikileaks supporters view the charges are politically motivated.

It looks to have surprised even Barlow, whose declaration of independence for cyberspace has been increasingly shared over Twitter by Anonymous supporters. He says he himself opposes distributed denial of service (DDoS) attacks aimed at knocking down sites, viewing them as anti-free-speech.

I support freedom of expression, no matter whose, so I oppose DDoS attacks regardless of their target, he told Reuters in an email. They're the poison gas of cyberspace.... All that said, I suspect the attacks may continue until Assange is free and WikiLeaks is not under continuous assault.

The exchange suggests cyber warfare could also become the preserve of small groups attacking each other as state actors.

POISON GAS OF CYBERSPACE

Alongside possible financial losses from sites being taken down, the potential reputational damage to firms is massive.

MasterCard has been mocked widely across the net as users lampooned its distinctive advertising slogans: Freedom of speech: priceless. For everything else, there's MasterCard.

This proves without question the power at people's fingertips --that there is high risk and vulnerability on the Internet, said John Walker, chief technology officer at cyber security company Secure Bastion.

If an organization like MasterCard with big computing power can have its site taken down then what about smaller organizations and ordinary people?

While most denial of service attacks use botnets to hijack other computers to overload websites, cyber security experts said Wednesday's attacks were different. Attackers were using their own computers, downloading software from Anonymous.

By midway through Wednesday afternoon, that software had already been downloaded some 6,000 times.

This whole... episode is causing a snowball effect, said Noa Bar Yosef, senior security strategist from Imperva. The more attention it is receiving, the more people who are joining the voluntary botnet to cause the DDoS.

WikiLeaks itself has also complained it has been under similar cyber attacks since shortly before it released the documents last week. While it has largely pointed to the United States and other governments, some say those attacks too may have been carried out by third parties.

Russian officials have long said that high profile cyber attacks against Estonia in 2007 and Georgia during its conflict with Russia in 2008 were in fact carried out by independent patriotic hackers rather than the government itself.

I think an interesting development is what we might term the 'Thomas a Becket' syndrome -- hackers deciding to act in ways they think benefit the country without being instructed to by a higher authority, said Nikolas Gvosdev, professor of national security at the US Naval War College.

Becket was the 12th century Archbishop of Canterbury murdered by four knights who reportedly overheard Henry II's complaints over him and took them as a royal wish he be killed -- an alarming historical example of unintended consequences.

(Additional reporting by William Maclean and Georgina Prodhan; Editing by Maria Golovnina)

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