Brand-new versions of the Netsky, Bagle, and Sober worm lines made it into the wild, with the Netsky variant, dubbed Netsky.q, the most troublesome of the trio.
Most anti-virus firms ranked Netsky.q, the seventeenth in the long-running series of pernicious worms, as a "medium" threat as it took off. Symantec, for instance, raised its rating early Monday morning from a "2" in its 1 through 5 scale to a "3", while Network Associates bumped up Netsky.q from "low" to "medium."
Netsky.q's distinguishing characteristics are a combination of social engineering first used by another worm, MyDoom, and an exploit of a three-year old vulnerability in older editions of Internet Explorer, Microsoft's popular Web browser.
"Netsky.q poses as a problem with e-mail," noted Vincent Gullotto, the vice president in charge of Network Associates' AVERT anti-virus research team. Using the same tactic as MyDoom, Netsky.q pretends to be a message alerting users of e-mail errors, with subject heads that range from "Mail Delivery failure" to "Server Error."