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.