What Does Anti-Virus Software Do?
Although details may vary between packages, anti-virus software scans files or your computer's memory for certain patterns that may indicate an infection. The patterns it looks for are based on the signatures, or definitions, of known viruses. Virus authors are continually releasing new and updated viruses, so it is important that you have the latest definitions installed on your computer.

What Does Your Company Need?
Your company needs a company-wide tool for detection of virus infections that updates automatically. To make anti-virus policies effective over the long run, have a process (and someone to oversee it) for reacting to virus infections. 

Check that your policy and procedures which cover employees home system as so many employees do company work on their home systems through telecommuting into the corporate network from their home systems via dialup or VPN over the Internet.

Each employee should scan his or her entire computer at home and at work periodically:

• Automatic scans - Depending what software you choose, you may be able to configure it to automatically scan specific files or directories and prompt you at set intervals to perform complete scans.

• Manual scans - It is also a good idea to manually scan files you receive from an outside source before opening them. This includes saving and scanning email attachments or web downloads rather than selecting the option to open them directly from the source scanning floppy disks, CDs, or DVDs for viruses before opening any of the files

Additional Resources
HANDOUT: National Cyber Alert System Tip:  Understanding Anti-Virus Software