A senior anti-spam activist is calling on law enforcement authorities to track down the perpetrators behind a widespread and sustained attack on anti-spam sites. The call, from Steve Linford of Spamhaus, comes along with fresh evidence that the assaults have been enabled by the infamous Sobig worm.
Earlier this week two anti-spam services, Monkeys.com and the Compu.Net "block list", announced their closure due to DDoS attacks, and other attempts by spammers to make their operation as difficult as possible.
Their closure follows an earlier decision to discontinue the popular if controversial SPEWS block list (which was run by Osirusoft.com) for similar reasons (see postings to news.admin.net-abuse.email for more info).
Linford tells The Reg that Spamhaus has been under constant "extremely heavy" DDoS attack since early July. He believes the attack against his site and others originates from Windows machines infected with the Sobig worm, controlled by spammers over IRC networks.
The Sobig worm is known to install Trojan code on infected PCs turning them into "zombies" capable of relaying spam messages or attacking other machines.
"Sobig has created a network of tens of thousands of zombie machines that have left a DDoS arsenal in the hands of spammers," Linford said.
Linford's theory is backed by a recent study by MessageLabs which shows a strong correlation between the origin of spam messages and the IP addresses of Windows machines infected by the Sobig, Fizzer or BugBear viruses. Matt Sergeant, senior anti-spam technologist at MessageLabs, said 70 per cent of the spam the company blocked came from open proxies. Half of these open proxies were established via Trojan infection with the rest being due to mistakes in setting up machines, he estimates.
According to Sergeant, a DDoS attack against anti-spam sites fits the profile of malevolent use for a Sobig-infected network of zombie clients. However, he adds, he has "no hard evidence" to prove this one way or the other.
Linford makes no such equivocations. He, like others, is convinced that Sobig was commissioned by spammers and is now been used as part of a sinister plan to force end users to spend more time wading through useless junk mail.
"Spammers have thrown this network of spam zombies against whatever stands in their path," he said.
According to Linford, Spamhaus has a large distributed network which has thus far been able to "absorb attacks", unlike smaller operations that have been "picked off one by one".
Thankfully other anti-spam organisations have picked up the roles of the spam fighters forced to close in recent weeks.
Because of this the attacks have failed to have a substantial effect of the absolute quantities of spam going through. But they have had an effect on the morale of anti-spam fighters, Linford concedes.
Linford is calling on law enforcements authorities to investigate who is controlling machines infected by the Sobig virus. Surveillance on IRC server channels can be used to identify the "zombie master" behind the criminal DDoS attacks of anti-spam organisations.
But only police have the ability and legal powers to carry out such tracking and surveillance operations, Linford argues.
"Government makes extensive use of anti-spam services and this network of zombie machines could easily be turned against government. The authorities need to find the people behind these attacks for their own interests, if for no other reason," Linford added. ®
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