SecurityTube

Polymorphic AutoRun Worm Evolves and Obfuscates

JB

Recently we have seen a spike in a Visual Basic 6-compiled AutoRun worm family. The family is both client- and server-side polymorphic. (For more on this family, refer to our VIL and Advisory entries.)

The W32/Autorun.worm.aaeh family usually gets on a victim’s machine through email spam, Blacole drive-by downloads, or downloads by BackDoor-FJW. From a behavioral perspective, it looks like any other thumb-drive infecting worm. It adds an autorun.inf file on all removable drives and network shares, has an icon resembling a folder icon to trick people into double-clicking it, and infects ZIP and RAR archives. What separates this worm from the rest, however, is the level of obfuscation and polymorphism that it employs.