Ifmember.exe - Windows 2003 Resource Kit Utility
IfMember is a command-line tool that checks whether the current user is a member of a specified group. It is typically used in Windows logon scripts and other batch files. IfMember uses its own process token to discover group membership, rather than querying the relevant domain controller each time it runs. While this has a significant performance benefit, it does mean that IfMember will only be aware of groups on the local computer, on the computer's domain, and on trusted domains.