Virus Name Risk Assessment
W32/Sasser.worm Corporate User : Medium
Home User : Medium
Discovery Date: 04/30/2004
Length: 15,872 bytes
SubType: Internet Worm
Minimum DAT: 4355 (05/01/2004)
Updated DAT: 4355 (05/01/2004)
Minimum Engine: 4.2.40
Description Added: 04/30/2004
Description Modified: 05/02/2004 11:45 AM (PT)
Method Of Infection
Variants / Aliases
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-- Update May 1st, 2004 --
The assessment of this threat has been upgraded to Medium due to an increase in prevalence
If you think that you may be infected with this threat, and are unsure how to check your system, you may download the Stinger tool to scan your system and remove the virus if present.
Note: Infected systems should install the Microsoft update to be protected from the exploit used by this worm. See:
This self-executing worm spreads by exploiting a Microsoft Windows vulnerability [MS04-011 vulnerability (CAN-2003-0533)]
The worm spreads with the file name: avserve.exe . Unlike many recent worms, this virus does not spread via email. No user intervention is required to become infected or propagate the virus further. The worm works by instructing vulnerable systems to download and execute the viral code.
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The virus copies itself to the Windows directory as avserve.exe and creates a registry run key to load itself at startup
CurrentVersion\Run "avserve.exe" = C:\WINDOWS\avserve.exe
As the worm scans random ip addresses it listens on successive TCP ports starting at 1068. It also acts as an FTP server on TCP port 5554, and creates a remote shell on TCP port 9996.
A file named win.log is created on the root of the C: drive. This file contains the IP address of the localhost.
Copies of the worm are created in the Windows System directory as #_up.exe.
A side-effect of the worm is for LSASS.EXE to crash, by default such system will reboot after the crash occurs. The following Window may be displayed: