|Assange loyalists have already taken credit for temporarily taking down websites of MasterCard and others [Reuters]
The website attacks launched by supporters of WikiLeaks show 21st-century cyber warfare evolving into a more amateur and anarchic affair than many predicted.
Attempts to silence WikiLeaks after the leaking of some 250,000 classified US state department cables seem to have produced something rather different - something of a popular rebellion amongst hundreds or thousands of tech-savvy activists.
"This is a cat and mouse game. It's not just the supporters of WikiLeaks but also some opponents that have been launching cyber attacks over the last few weeks," Kevin Anderson, a technology journalist and New Media expert, told Al Jazeera on Thursday.
"It is definitely a cyberwar where people are taking sides and putting their computers where their alliances are," he said.
The cyberwar began after MasterCard, PayPal, Visa and a Swiss bank blocked payments to WikiLeaks, which runs on donations. These companies, along with Amazon, which banned WikiLeaks from using its servers, are thought to have given in on a US pressure.
In retaliation, a hacker group calling itself Anonymous, launched "Operation Avenge Assange", referring to WikiLeaks founder Julian Assange - targeting the credit card companies, with what are called "denial of service" (DDoS) attacks.
Meanwhile, a 16-year-old boy has been arrested in the Netherlands, and has reportedly admitted attacking Visa and MasterCard's websites after they blocked donations to Wikileaks.
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.
|New Media expert Kevin Anderson speaks to Al Jazeera about 'Operation Payback'
The group used social networking site Twitter to co-ordinate attacks on websites belonging to entities it views as trying to silence WikiLeaks.
Twitter and Facebook have suspended the accounts of the "Anonymous" group.
"The first serious info war is now engaged," John Perry Barlow, the former Grateful Dead lyricist and founder of the Electronic Frontier Foundation told his followers on Twitter last week.
"The field of battle is WikiLeaks. You are the troops."
Barlow's "declaration of independence for cyberspace" has been increasingly shared over Twitter by Anonymous supporters.
However, attacks aimed to denial of service are not universally supported by pro WikiLeaks groups. Barlow himself opposes such attacks, 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. "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."
Alongside possible financial losses from sites being taken down, the potential damage to firms is significant.
MasterCard has been mocked widely across the internet 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," John Walker, the chief technology officer at cyber security company Secure Bastion, said.
|MasterCard and other payment firms have severed ties with WikiLeaks in recent days [EPA]
While most denial of service attacks use so-called "botnets" to hijack other computers to overload websites, cyber security experts said Wednesday's attacks were different.
"Botnet" is a programme that overloads a website by sending huge numbers of "information requests" to it.
Attackers were using their own computers, downloading software from Anonymous. By Wednesday afternoon, that software had already been downloaded some 6,000 times.
"This whole episode is causing a snowball effect," Noa Bar Yosef, the senior security strategist from Imperva, said. "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 as the source, some say those attacks may have been carried out by third parties.
Whether the world has entered a "cyberwar" or "info war" is too soon to tell, however, the battles currently being fought on the internet bear no comparison to conventional warfare.
Al Jazeera is not responsible for the content of external websites