WM/Sig is a simple macro virus which contains a macro called "signature". This virus is not widespread.
Sig activates by adding a single line saying "WIN" to the end of AUTOEXEC.BAT file.
[Katrin Tocheva, F-Secure]
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.