The activists behind Operation Payback have come up with a new way to annoy corporations that have severed their ties with WikiLeaks: bombard them with faxes.
In online chats, group members have posted the fax numbers for about a half-dozen corporations and are calling volunteers to fill up the fax machines, using free online fax services such as MyFax.com and FaxZero.com. They're recommending that people use anonymizing software such as the Tor Project to access these sites, so that they cannot be traced by authorities.
The latest development comes after websites belonging to Visa, MasterCard International and PayPal have been hit with distributed denial of service attacks, launched by Operation Payback in an effort to pressure the companies to resume payment processing for WikiLeaks.
"The enemy is adapting to our strategies, Gentlemen, but they are a lumbering bureaucracy. We can change faster," the group said in a note being circulated on its chat servers Monday.
Activists are encouraged to send images of Guy Fawkes or random excerpts from WikiLeaks' leaked U.S. Department of State cables to the fax numbers.
Paul Mutton, a security analyst with the Netcraft Web monitoring firm, said that it's not clear how damaging the fax campaign has been. Within hours of its launch, the online chatroom set up to coordinate the fax attacks had 73 members, he said.
The loosely organized group behind Operation Payback, called Anonymous, has tried this tactic before. In January 2008 it encouraged members to fax-bomb the Church of Scientology, another of its favorite targets.
Although Operation Payback's attacks have gained a lot of media attention, they have had little effect on their targets' core businesses. MasterCard said that some of its SecureCode transaction processing was slowed down last week, but the back-end transaction systems used by Visa and MasterCard have been unaffected by the attacks. Paypal's Paypal.com website went down on Thursday, but the company said that the servers it uses to process transactions were virtually unaffected.
Meanwhile, Operation Payback has become a top news story. "It's certainly drummed up a few news headlines," Mutton said.
The attacks aren't difficult to thwart, but they do cost money as companies have to scramble and harden their infrastructure. In the meantime, they make it hard for customers to reach the company. "Those websites are usually the first port of call for anyone who wants to use those online services," Mutton said.
The fax attacks look like they could be an annoyance, and they appear to be having some effect. Anonymous has posted a list of numbers that it says are no longer responsive. One number, the Visa fax number listed by Yahoo Finance, was disconnected Monday afternoon. A Visa spokesman did not immediately have a comment on the situation, but Visa seems to be aware of the problem. A call center operator asked for Visa's fax number on Monday said simply: "I cannot provide that information."
Robert McMillan covers computer security and general technology breaking news for The IDG News Service. Follow Robert on Twitter at @bobmcmillan. Robert's e-mail address is robert_mcmillan@idg.com