MemorY has some very good points, but you didn't say if it is from remote access or people just (physically) logging on the actual computer. If it is the later, simply password protect it.
\"Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, Champagne in one hand - strawberries in the other, body thoroughly used up, totally worn out and screaming WOO HOO - What a Ride!\"
Author Unknown