After the announcement that the World’s biggest credit card and online payment companies would no longer process payments funding WikiLeaks, an international group of hackers, called Anonymous have targeted Visa, MasterCard and PayPal in a series of cyber attacks dubbed “operation payback”. The MasterCard secure code was stopped for 6 hours yesterday which affected hundreds of thousands of shoppers worldwide. Visa also went down after it was targeted in the attacks. This movement comes on some of the busiest online shopping days of the year in the run up to Christmas which will have a substantial impact on online retailers.

5000 ‘hacktivists’ are said to be behind the cyber attacks. Around 2000 computers bombarded the Visa Website last night, bombarding the host computers with requests for information, causing them to crash.

The attack on MasterCard brought down parts of its website. Shoppers were affected when they were taken to the Securecode website run by MasterCard, which was not authorising transactions so payments could not be completed.

In an interview with BBC Radio, an unofficial spokesman for the group going by the name of “Coldblood” said: "The campaign is not over. It's still going strong, more and more people are joining and helping in."

Anonymous claimed Twitter was censoring the #WikiLeaks and #cablegate hashtags in its trends after coming under government pressure. Twitter however officially addressed this in its blog saying the terms were not as popular as previous and thus have not been picked up by the algorithm. The group was kicked off Twitter and Facebook over night for breeching terms of use, although it has reappeared on Twitter under a new name. It is thought Twitter will be the next target after Anonymous posted a status saying 'Twitter you're next for censoring WikiLeaks discussion.'

Anonymous however wrote on its website “While we don't have much of an affiliation with WikiLeaks, we fight for the same reasons. We want transparency and we counter censorship.”