Casstub.exe is an adware program Adware.CasinoClient. Casstub.exe displays advertisements. Casstub.exe monitors user Internet activity and private information. It sends stolen data to a hacker site. Related files: %ProgramFiles%\Cas\Client\casclient.exe %ProgramFiles%\Cas\Client\casmf.dll %ProgramFiles%\CasStub\casstub.exe More info: http://securityresponse.symantec.com/avc... Removal: Kill casstub.exe process and remove casstub.exe from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.