WASHINGTON (AFP) - Anonymous, the hacktivist group behind cyber attacks on Visa.com, Mastercard.com and other websites, vowed Wednesday to extend their campaign to anyone with an anti-WikiLeaks agenda. In an online chat with Agence France-Presse, organisers of Anonymous said thousands of volunteers were taking part in their defence of WikiLeaks and its founder Julian Assange, whom they described as a free-speech martyr. We started off with a small amount of users (below 50), they said. Now, we are at around 4,000. We recruit through the Internet, that means, everywhere: image boards, forums, Facebook, Twitter... you name it, were using it, they said, adding that members are drawn from all over the world. Anonymous members launched their first distributed denial of service, or DDoS, attack on Saturday, taking down PayPals blog, ThePayPalBlog.com, for at least eight hours. Since then, they have taken down the websites of Visa, Mastercard and the Swiss Post Office bank for severing ties to WikiLeaks and the website of the Swedish prosecutors office for pursuing Assange on allegations of sex crimes. Members of Anonymous also took aim on Wednesday at the websites of US conservative standard bearer Sarah Palin and US Senator Joe Lieberman, who called for US companies to withdraw technical support for WikiLeaks. Palin for her part described Assange, whose release of thousands of secret US diplomatic cables has sparked an international furore, as an anti-American operative with blood on his hands. In the online chat with AFP, the Anonymous organisers declined to identify future cyber targets but said anyone that has an anti-WikiLeaks agenda is within our scope of attack. They said the defence of WikiLeaks was an extension of Operation Payback, a movement which began on Internet messageboard 4Chan in September. Operation Payback involved cyber attacks on the websites of the Motion Picture Association of America, Recording Industry Association of America and others over their vigorous copyright protection efforts. Operation Payback stands for free speech and no censorship, which is also what Assange is going for, the Anonymous organizers said. Whether we see him as a crusader or martyr, his goals are ultimately ours. When we think we made our point (eg WikiLeaks accepted as whistleblower, without fear that they will be prosecuted), we will return to fighting 'copywrong, they said. Anonymous had been announcing their moves on Twitter at @Anon_Operation but their Twitter feed was suspended late Wednesday and their Operation Payback page on Facebook was removed. Sean-Paul Correll, a threat researcher at PandaLabs, the malware detection laboratory for computer security firm Panda Security, said Anonymous are very resourceful and he expects their activities to go beyond just DDoS attacks. In a classic DDoS attack, a botnet of zombie computers, machines infected with viruses, are commanded to simultaneously visit a website, overwhelming its servers, slowing service or knocking it offline completely. I expect a laundry list of targets, Correll said. Theyll research security vulnerabilities on a website. Theyve defaced websites in the past so I expect to see all sorts of things coming in the future. Correll, who has been following Anonymous from what he called Day One, said the group doesnt have a central authority or hierarchical structure. People describe it as having a kind of hive mind mentality, he said.