The latest variant of the Klez worm sometimes chooses to hitch a ride on sensitive documents, resulting in victims" confidential information spreading with the malicious program, Russian antivirus firm Kaspersky Labs said Friday.
Known as Klez.g, Klez.h and Klez.k, depending on the security advisory, the newest incarnation has spread worldwide, sending itself in e-mail messages with infected documents attached.
Most antivirus vendors, including Symantec, McAfee and Sophos, have offered Klez.H patches since Wednesday.
"Klez.h poses a special threat: The worm scans the disks of an infected computer and, depending on a set of conditions, attaches a file to each infected e-mail it distributes," stated the advisory.
Text, HTML (Hypertext Markup Language), Adobe Acrobat and Excel files are included in the types of documents that the virus can forward, but other files that the worm could attach--such as JPEG and MPEG files--are less likely to contain important information.