Hackers in support of WikiLeaks have brought down the websites of credit-card giants Visa and MasterCard in the ongoing cyber-war between sympathisers of the whistle-blower site and firms trying to stifle it. During Christmas season when online shopping is on rise, pro-WikiLeaks activists launched cyber assaults -- code-named "operation payback" -- a few days ago and succeeded in temporarily arresting the websites of Visa, MasterCard, Swiss payment transaction company PostFinance and PayPal.
The centre of their strategy is to cripple these websites by bombarding them with millions of bogus visits. Online retailing giant Amazon reportedly also had to fend off a number of attacks by WikiLeaks' sympathisers on Thursday.
These companies withdrew services from Julian Assange's site after it leaked secret US diplomatic cables, causing major embarrassment for Washington. Wigglers has been using its accounts with these institutions for collecting donations, a major source of the website's income.
CEO of PayPal Osama Beider has admitted that his company closed the whistle-blower's account following pressure from the US government. The cyber attacks are also motivated by the campaigners' anger over the arrest of Assange in London over alleged sex crimes committed in Sweden.
He is awaiting a hearing in the British capital on whether the site's founder should be extradited to Sweden to stand trial there. The attackers have reportedly temporarily brought down the website of the Swedish government.
Meanwhile, a 16-year-old boy was arrested in the Hague on Wednesday in connection with the attacks. He admitted of participating in the attacks against Visa, MasterCard and PayPal, police have claimed.
Cyber security researchers say the pro-WikiLeaks activists, an alliance of hacker groups Anonymous and 4chan, have been launching their retaliatory attacks through distributed denial of service (DDoS) and most of them were using the Low Orbit Ion Cannon Tool (LOIC).
They brought down the PostFinance website with a LOIC regiment involving around 400 computers, while several thousand of them were needed to cripple the Visa website, according to German computer journal 'ct Magazine'.
'Hacktivists' are building up their army of computers that hackers control remotely (botnet) to launch new attacks, the magazine said quoting security researchers. Till now, their attacks have been launched predominantly by volunteers, who manually control the LOIC, which is an open-source tool.
In the past few days, there has been a surge in demand for the LOIC and thousands of copies were downloaded, indicating that the activists are bracing to intensify their cyber war, experts said.
The supporters of WikiLeaks said in a 'manifesto' that their intension is not to destroy the infrastructure of the concerned organisations, but only to "disturb" their internet presence.
In an appeal on their websites, they have called upon the online community to download the LOIC and join them in their campaign against the websites hampering the work of WikiLeaks.
