McAfee through its McAfee AVERT (Anti-virus and Vulnerability Emergency Response Team) has raised the risk assessment to Medium-on-Watch on the recently discovered W32/Bagle.af@MM, also known as Worm_Bagle.af (TrendMicro) or W32.Beagle.AB@mm (Symantec). This new variant is a mass-mailing worm that comes in the form of a password-protected .ZIP file, with the password included in the message body as plain text or within an image.

The Bagle.af worm contains its own SMTP engine to construct outgoing messages. It harvests addresses from local files and then uses the harvested addresses in the 'From' field to send itself. This produces a message with a spoofed From address. The attachment can be a password-protected zip file, with the password included in the message body. It contains a remote access component (notification is sent to hacker) and uses mutex names from variants of W32/Netsky to prevent those W32/Netsky variants running on infected machines.

After being executed, Bagle.af copies itself into the Windows System directory (C:\WINNT\SYSTEM32\sysxp.exe). The worm also creates sysxp.exeopen and sysexpopenopen in this directory to perform its functions. The following Registry key is added to hook system startup:

-- HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run "key" = "C:\WINNT\SYSTEM32\sysxp.exe"

Bagle.af also copies itself to folders that have the phrase shar in the name, such as common peer-to-peer applications; KaZaa, Bearshare, Limewire, etc. The worm then emails itself to addresses found on the infected host as a password protected .ZIP file with the password included in the message body.

According to Symantec, the worm opens a backdoor on TCP port 1080. The email will have a variable subject, and it'll notify the author on a variety of websites, listed on Symantec's bulletin. The worm will also stop any processes related to personal firewalls or anti-virus software.