New Bagle Worm Variant Can Run Without Launching Attachment

[InfoSec News <isn () c4i org>]

http://www.eweek.com/article2/0,1759,1550841,00.asp

By Larry Seltzer 
March 18, 2004   

A series of new variants of the prolific Bagle worm has raised alarms
in the security community through an innovative infection mechanism:  
The e-mail message in which the variants arrive may have no file
attachment, and it's possible for a user to become infected without
having to launch one.

The message includes a Windows ActiveX control and uses a
vulnerability announced and patched by Microsoft Corp. in August and
another problem from last October. The most recent Cumulative Security
Update for Internet Explorer also includes a fix for the more recently
discovered flaw.

The ActiveX control does not contain the actual worm, according to
McAfee Security. Instead, it creates and runs a VBScript on the
system, which downloads and executes the worm from one of a list of IP
addresses. According to McAfee, as of 06:45 PST on March 18, "The
majority of the 590 IP addresses seen have been closed down. At the
time of writing, 39 were still responding."

Antivirus companies have become out of sync with each other with
respect to Bagle variants. Panda Software refers to the new ones as
Bagle.P, Bagle.Q and Bagle.R., with Bagle.Q as the most serious one.  
Panda reports that the worm "infects PE files [which are standard
Windows .EXE programs], downloads a file from the Internet and ends
processes belonging to security applications." Kaspersky Labs Int.'s
analysis of the code says that the program attempts to infect PE files
but fails to do so due to an error in the code.

According to Trend Micro Inc.'s analysis of the worm, it also spreads
through the conventional e-mail attachment mechanism, as well as
through peer-to-peer networks and shared folders. Symantec Corp. calls
the three worms Beagle.R, Beagle.S and Beagle.T but did not have
analysis ready for them as of this story's posting.

The ActiveX infection mechanism requires that the e-mail client permit
ActiveX controls to run in HTML e-mail. Microsoft e-mail clients have
disallowed this feature by default for several years.

All of the major antivirus companies claim to have detection
definitions available for the worms. However, they haven't necessarily
prepared disinfection routines.
 


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