Panda Software warns that the users can detect and disinfect the new worm with an updated antivirus, but it's also needed to install the patch provided by Microsoft to be sure the virus do not infects again the computer. The vulnerability used by Sasser.A was published by Microsoft last week in the bulletin MS04-011 with the correspondent solution. Panda Software customers already have the updates to detect and disinfect this new worm.
In addition, the users can scan their computers on line for free with the ActiveScan solution, available in the company web page: http://www.pandasoftware.com More Information about this threat or other ones, is available in the virus encyclopedia, at http://www.pandasoftware.com/virus_info/encyclopedia/
Sasser.A behavior is similar to Blaster. The worm scans random IP addresses until it finds systems with this vulnerability. Once found, it copies itself in Windows directory with the name AVSERVE.EXE and creates the following registry entry, to ensure it is launched when the system is booted:
avserve.exe = %windir%avserve.exe
In addition, the vulnerability uses a buffer overflow to make the LSASS.EXE application crash. Because of this, the system can fail.