Sasser.C is an Internet worm spreading through the MS04-011 (LSASS) vulnerability.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.
If the infection is in a local network, please follow the instructions on this webpage:
To manually disinfect an infected system, first apply the Microsoft patch MS04-011, then use Task Manager to kill the "avserve2.exe" process, then delete the file AVSERVE2.EXE from your Windows directory and reboot. For step-by-step instructions, see Microsoft's site: https://www.microsoft.com/security/incident/sasser.asp#steps
Sasser.C is a variant of Sasser.B, with identical length. Main difference is that this version starts 1024 processes to scan for new vulnerable hosts, instead of 128 processes.
For more details, see the description of Sasser.B