Userx.exe is a mass-mailing worm W32.Mytob.JF@mm. Userx.exe opens a back door on TCP port 6677. Userx.exe tries to terminate antiviral programs installed on a user computer. Related files: %System%\userx.exe Adds the value: "Msn Update Service" = "userx.exe" to the Windows startup registry keys. More info: http://securityresponse.symantec.com/avc... Removal: Kill userx.exe process and remove userx.exe from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.