isnsys.dll is a Trojan.Chast-A. isnsys.dll opens a back door. isnsys.dll monitors user Internet activity and private information. It sends stolen data to a hacker site. Related files: %Windows%\win16svc.exe %Windows%\isnopt.dat %Windows%\isnsys.dll %Windows%\isnsys32zx.dll More info: http://www.sophos.com/virusinfo/analyses... Removal: Remove isnsys.dll from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.