Zotob arrests throws open trade in compromised PCs

One of two men arrested last week over the Zotob worm outbreak has been linked to the creation of 20 other viruses.

Farid Essebar, 18, a Russian-born Moroccan resident, was arrested by investigators last Thursday, less than two weeks after Zotob worms exploited recently-discovered Windows flaws to disrupt high profile organisations around the world. Essebar was allegedly paid by his supposed accomplice, Atilla Ekici, to create the worms. Ekici has been arrested in Turkey by police investigating the case.

Essebar is believed to use the nick-name "Diabl0", a phrase embedded inside the Zotob-A worm. Sophos researchers have determined that over 20 other viruses include the "Diabl0" handle, including numerous variants of the Mytob worm (a code cousin to Zotob) as well as a MyDoom variant, MyDoom-BG.

"Until the authorities recover source code from the suspect's computers there won't be any hard evidence but the use of the 'Diabl0' handle is circumstantial evidence of linkage. Virus writers tend to sign their work like graffiti artists," said Graham Cluley, senior technology consultant at anti-virus firm Sophos.

"To the untrained eye the Mytob and Zotob worms can appear quite different: one group of viruses travels via email, the other mostly by exploiting a Microsoft security hole. But when examined by an experienced virus analyst, the similarities become clear. It appears whoever wrote Zotob had access to the Mytob source code, ripped out the email-spreading section and plugged in the Microsoft exploit," he added.

Sophos reckons several people have access to the Mytob source code - so last week's arrest will at best only slow down rather than curtail the production of fresh variants. Anti-virus firm F-Secure agrees with Sophos that Diabl0 is the likely author of several of the Mytob variants since February this year. "However, he's not behind all of them," said Mikko Hyppönen, director of anti-virus research at F-Secure. "There's around 70 known variants of Mytob and practically all of them create botnets of the infected machines. Some of these botnets have been controlled by unrelated groups, such as Blackcarder."

F-Secure has found Mytob variants written after Essebar's arrest, backing up their theory that multiple virus authors are involved in distributing the malware strain. But there's little doubt "Diabl0" is a significant player. Some earlier Mytob variants downloaded additional components from a site associated with the 0x90-Team, an underground gathering site for bot authors. "Diabl0 aka Farid Essebar was associated with 0x90-Team," Hyppönen writes in an entry to F-Secure's weblog which notes the 0x90-team.com was defaced last weekend by hackers objecting to the activities of bot authors.

Earlier this month separate groups of hackers released a barrage of worms in a battle to seize control of Windows PCs that remain vulnerable to the now infamous Windows Plug-and-Play vulnerability exploited by Zotob. Fragments of evidence suggest a group called m00p is creating IRCBot variants that compete with Zotob variants created by 0x90-Team over the control of vulnerable Windows PCs. ®