The top selling software package in the first half of 1999 was Norton AntiVirus 5.0 from Symantec. Not far behind in seventh position was McAfee VirusScan 4.0 Classic from Network Associates. The latter scans all incoming mail for known viruses automatically, rather than waiting to be prompted when a suspicious attachment is included with an e-mail message.
The appearance of these products on the software best-seller list compiled by PC Data reflects the increasing awareness of PC users that viruses are a serious threat. While no one has tabulated the losses incurred by individual users, a survey of businesses ascertained that losses during the first half of 1999 were at least $7.6 billion, including both repair costs and lost productivity. Over 20 percent of the businesses lost money or productivity because of the Melissa virus-which first appeared on March 26, 1999 and did most of its damage in just three days. It is estimated that a total of 100,000 computers were infected.
The effect of the Melissa virus was to stimulate anti-virus software sales and more care in downloading the regular updates offered by most vendors of anti-virus software. When the Chernobyl virus hit in early May, its impact in North America was minimal, fewer than 3,000 computers. In foreign countries where computer users had not been snapped to attention by Melissa, nearly 1.5 million competitors were infected by the Chernobyl virus.
An anti-virus package can be effective even before a virus is identified and specifically addressed by the software. This is accomplished by looking for characteristics common to many viruses. When these characteristics are present, a user is warned of a potential virus. The Chernobyl virus had a "signature" which had some of the same characteristics as Melissa, therefore, many anti-virus products raised an alarm.
Libraries should place a high priority on anti-virus protection. Public Internet machines in libraries are particularly vulnerable. Libraries should not only purchase and install anti-virus software on all public Internet machines (as well as staff machines), but they should download updates from the Web site of the anti-virus software vendor to provide protection against new viruses at least once a month, preferably twice a month. About 300 new computer viruses appear each month. Most vendors post updates within days of new attacks.