Yak_tw.dll is a Trojan Backdoor.Graybird. Yak_tw.dll injects itself into all running processes. Related files: %Windir%\yak_tw.exe %Windir%\yak_tw.DLL %Windir%\yak_twKey.DLL %Windir%\yak_tw_Hook.DLL Adds the value: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\yak tw HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\ENUM\ROOT\LEGACY_YAK_TW to the Windows startup registry keys. More info: http://securityresponse.symantec.com/avc... Removal: Remove yak_tw.DLL from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.