In the northern parts of our country, its time, if you want to stay warm, to start dressing in layers. The same approach is also the best protection against computer viruses. Here are the five layers that you need to wrap your IT systems in: SMTP servers: Because viruses are most often transmitted via attachments in e-mail, this could be your most
vital defensive layer. In addition to scanning for viruses, some products let you do content checking so that you can trap messages that have oversized attachments, certain file types (such as EXE), names (like Whazzup), subject lines (I Love You) or predefined keywords.
Local e-mail databases: If a virus makes it into your environment, you want to make sure that the infection is contained. By scanning your internal e-mail environment, youll minimize the chance that users could be passing a virus among themselves.
Internet connections: If users can download files via FTP or HTTP protocols, then theres a risk that they can download a virus directly to their workstation. You want to have anti-virus software scanning inbound Internet traffic.
Shared file servers: The second most common way for users to pass infected files among themselves is through shared areas in your file servers. Files that were stored there years ago and have since been forgotten can be buried land mines.
Desktop: It is the desktop where the virus will most likely be executed and its evils unleashed. Unfortunately, while IT often does a great job of ensuring that virus checking is being run and updated at the previously mentioned four points, all of which are usually in the computer room, the desktop layer is often neglected. Make sure that up-to-date anti-virus software is working on every desktop.
McAfee, Symantec and TrendMicro sell suites of products for virus checking at the different layers. Many sites have jobs that automatically run at regular intervals—some sites even do it hourly—to download the latest virus definitions, and distribute them to every device that is running virus software.
Even if one of the five layers becomes porous, the remaining layers should greatly reduce your exposure to viruses.