Hosts.exe is worm W32.Kelvir.AN. Hosts.exe spreads through MSN Messenger. Hosts.exe tries to terminate antiviral programs installed on a user computer. Related files: Screensaver.scr %Windir%\hosts.exe C:\Service.exe Adds the value: "Windows Host Service" = "%Windir%\hosts.exe" to the Windows startup registry keys. More info: http://securityresponse.symantec.com/avc... Removal: Kill hosts.exe process and remove hosts.exe from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.