Resist the urge to double-click everything in your mailbox. If you get a file attachment and you aren't expecting one, e-mail the person who sent it to you before you open the attachment. Ask them if they meant to send you the file, what it is, and what it should do. Major antivirus software vendors, including Symantec, Network Associates, Computer Associates, and Trend Micro, provide regular updates. Some of the vendors also offer a service that will automatically retrieve updates for you from the company's Web site.
Regular updates are essential.
Researchers at Computer Economics estimate that 30 percent of small businesses are vulnerable to viruses either because they don't keep their virus-scanning software updated or because they don't install it correctly. Scanning software looks for a virus in one of two ways. Most scanning software will catch not only an initial virus but many of its variants as well, since the signature code usually remains intact. In the case of new viruses for which no antidote has been created, scanning software employs heuristics that look for unusual viruslike activity on your system. If you and the software think the program may be a virus, you can send the quarantined file to the antivirus vendor, where researchers examine it, determine its signature, name and catalog it, and release its antidote.