Following the arrest of Wikileaks founder Julian Assange, several Wikileaks supporters have launched "cyber attacks" on the websites of companies who withdrew services from the whistle blowing website. Those targeted include MasterCard, Visa, and a Swiss bank.

WikiLeaks appears to have some serious cyber defense mechanisms.

On Wednesday, a group operating under the label "Operation Payback", claimed responsibility for cyber attacks on several companies who they accuse of acting against Wikileaks, and its founder Julian Assange.

In a further twist, a hacking group known only as "Anonymous", is distributing software tools to allow anyone with a computer to join in the attack, which has been dubbed "Operation Payback".

Rob Cotton, Chief Executive, NCC Group, said, "It's become more sinister because they have asked members of the public to join into this by downloading."

Though cyber attacks are not unusual for financial companies, this case is different.

Alexis Mifsud, Cheif Executive, Ixaris, said, "However, in this case, they are being targeted by effectively people who see themselves as activists and who want to make a point that they stand for freedom of information that WikiLeaks brings."

Both Mastercard and Visa say cardholders' accounts are not at risk, and people can continue using their credit cards as normal. The hackers appear to use software to trigger multiple requests to the websites, which then fail due to being overloaded.

A string of US-based companies, including Amazon and Ebay, have cut ties to WikiLeaks, following intense pressure by the US government.

The members of "Operation Payback" and "Anonymous" are keeping their individual identities and locations a closely guarded secret.