Hiding a DL

Q; I want to hide a distribution list (DL) from the Microsoft exchange Server Globel address list (GAL).The options Hide from address book and Hide Membership from address book appear on the address tab for the user's mail box in Microsoft exchange Administrator.What's the difference between these options?

A; If you choose Hide from address book,The DL won't appear in the GAL,So you must know the Exact DL name to send a message to the list,If you choose hide Membership from address book then the DL appears in the GAL, but the list's membership remains hidden.If you right -click the DL and select properties,no names appear in the members area.