There are no viruses that can t be found by properly functioning antiviral software, unless the virus is so new that its signature is not in the virus definition file. Update your virus definition files often. Do not open unknown messages in Microsoft Outlook. Do not run programs attached to email without virus checking them. User training and rules Train users to follow the rules.
Enforceable rules are best.
For example, make certain all users have antiviral software and current virus definition files. Then make sure it is active on their computers.