Sobig worm getting bigger

IDG News Service - A new computer worm, Sobig, is spreading on the Internet, according to alerts posted by a number of antivirus software companies.
Sobig uses e-mail and shared network folders to infect machines running Microsoft Corp.'s Windows operating system, according to information from Helsinki, Finland-based antivirus company F-Secure Corp.
The worm arrives in e-mail messages from a single sender, big@boss.com, and is stored in attached executable files with names such as Sample.pif, Untitled1.pif and Movie_0074.mpeg.pif, according to F-Secure.
When opened, the worm places a copy of itself into the Windows folder on the infected machine, creates a process to run the worm program and modifies the Windows registry so that the worm program will be launched whenever Windows is started.
Once it has infected a machine, the worm searches for e-mail addresses in a variety of text files on the computer's hard drive. Those addresses are used to send out more copies of itself. Sobig also searches for any shared folders on networks that the infected machine may have access to and places a copy of itself in any network folder it can access.
Although the new worm doesn't appear to steal sensitive information from the computers it infects, F-Secure said antivirus companies warned that the worm connects to a Web site hosted by Yahoo Inc.'s GeoCities, from which it tries to download and execute other files.
The GeoCities Web page used by Sobig was modified recently to instruct the worm to download a Trojan program known as Backdoor.Delf that gives the virus writer and others control of infected machines, according to Mikko Hypponen, manager of antivirus research at F-Secure.
GeoCities has been notified about the page by F-Secure as well as the CERT Coordination Center in Pittsburgh, according to Hypponen. Yahoo wasn't immediately available to comment on the Sobig worm.
The worm first came to the attention of antivirus companies last Thursday and began spreading slowly, Hypponen said. In recent days, however, it has spread more rapidly. As of Tuesday, F-Secure gave the worm a Level 2 ranking, indicating "large infections" and putting it in a category with well-known predecessors such as the Klez worm.
Other antivirus companies upgraded their threat ratings for Sobig, as well. On Monday, Symantec Corp.'s Security Response upgraded Sobig from a Category 2 to a "moderate" Category 3 threat.
The success of Sobig since it first appeared surprised Hypponen, who said Sobig is a comparatively simple worm that lacks many of the sophisticated features that allow the new generation of viruses to spread.
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