Mcsmss.exe is a Backdoor Trojan.Repsamo. Mcsmss.exe monitors user Internet activity and private information. It sends stolen data to a hacker site. Related files: %System%\mcsmss.exe Adds the value: "cmssSystemProcess" = "%System%\mcsmss.exe" to the Windows startup registry keys. More info: http://securityresponse.symantec.com/avc... Removal: Kill mcsmss.exe process and remove mcsmss.exe from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.