'Hacktivists' to continue digital sit-in over net freedom battle

The loose-knit group, known as Anonymous, has disrupted sites belonging to finance giants including MasterCard and Visa by bombarding their websites with millions of bogus visits during a campaign called "Operation Payback".

Their blog post vowing to fight any organisation which supports censorship came as WikiLeaks' payment processor, DataCell, said it was preparing to take legal action against the credit card companies over their refusal to process donations.

DataCell chief executive Andreas Fink said: "It is obvious that Visa is under political pressure to close us down. We strongly believe a world-class company such as Visa should not get involved in politics and just simply do their business where they are good at. Transferring money."

In a blog linked to its Twitter account, Anonymous wrote: "The message is simple: freedom of speech. Anonymous is peacefully campaigning for freedom of speech everywhere in all forms."

Anonymous launched a series of so-called distributed denial-of-service (DDoS) attacks against various websites including the credit card companies, PayPal, and the Swedish prosecutor's office, which is acting in the legal case against WikiLeaks founder Julian Assange.

Assange is on remand in London after being arrested and refused bail over sexual offence charges he is facing in Sweden.

John Mueller, PayPal's general counsel, has said WikiLeaks' account will remain restricted but the firm will release all remaining funds to the site's account.

DDoS attacks, which are illegal in the UK, involve overloading a website with high numbers of requests so it stops working.

Anonymous said it was leading a "peaceful campaign" and denied being a terrorist or vigilante organisation.

A statement on the WikiLeaks website read: "These denial of service attacks are believed to have originated from an internet gathering known as Anonymous. This group is not affiliated with WikiLeaks."

Mike Prettejohn, a director of security firm Netcraft, which is monitoring the attacks, said: "They are all pretty difficult targets. Amazon has a huge infrastructure. It's a very technically sophisticated company.

"But we have already seen disruption at Visa and PayPal."