There are a few ways to remove and prevent this worm from coming back
Can you ge more info from Microsoft here:
http://www.microsoft.com/security/incident/sasser.asp
You can also try these removal tools:
Symantec's removal tool
Network Associates removal tool
Or you could try removing it manually:
1. End the malicious process.
2. Disable System Restore (Windows Me/XP).
3. Update the virus definitions.
4. Run a full system scan and delete all the files detected as
W32.Sasser.Worm.
5. Reverse the change made to the registry.
For details on each of these steps, read the following instructions.
1. To end the malicious process
To end the malicious process:
a. Press Ctrl+Alt+Delete once.
b. Click Task Manager.
c. Click the Processes tab.
d. Double-click the Image Name column header to alphabetically sort
the processes.
e. Scroll through the list and look for the following processes:
- avserve.exe
- any process with a name consisting of 4 or 5 digits
followed by _up.exe (eg 74354_up.exe).
f. If you find any such process, click it, and then click End
Process.
g. Exit the Task Manager.
2. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you
temporarily turn off System Restore. Windows Me/XP uses this feature, which
is enabled by default, to restore the files on your computer in case they
become damaged. If a virus, worm, or Trojan infects a computer, System
Restore may back up the virus, worm, or Trojan on the computer.
Windows prevents outside programs, including antivirus programs, from
modifying System Restore. Therefore, antivirus programs or tools cannot
remove threats in the System Restore folder. As a result, System Restore has
the potential of restoring an infected file on your computer, even after you
have cleaned the infected files from all the other locations.
Also, a virus scan may detect a threat in the System Restore folder even
though you have removed the threat.
Windows XP:
1.. Click Start > Programs > Accessories > Windows Explorer
2.. Right-click My Computer, and then click Properties.
3.. Click the System Restore tab.
4.. Check the "Turn off System Restore" or "Turn off System Restore on all
drives" check box.
5.. Click Apply.
6.. This will delete all existing restore points. Click Yes to do this.
7.. Click OK.
8.. Proceed with what you need to do.
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Note: When you are completely finished with the removal procedure and are
satisfied that the threat has been removed, re-enable System Restore by
following the instructions in reverse
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3. Update your Virus Definitions from NAI or Symantec
4. Scan and delete the infected files -
Run a full system scan.
If any files are detected as infected with W32.Sasser.Worm, click Delete.
5. To reverse the change made to the registry
a. Click Start, and then click Run. (The Run dialog box appears.)
b. Type regedit
Then click OK. (The Registry Editor opens.)
c. Navigate to the key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
d. In the right pane, delete the value:
"avserve.exe"="%Windir%\avserve.exe"
e. Exit the Registry Editor.
