lsasss.exe is a process which is registered as w32/Sasser.E Worm. It takes advantage of the Windows LSASS vulnerability, which creates a buffer overflow and instigates your computer to shut down.
To see more information about this vulnerability please look at the following Microsoft bulletin: http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx.
This process is a security risk and should be removed from your system. Please see additional details regarding this process.