Health care for computers: protect your computer and your business from viruses.

Computer viruses are commonplace. According to a recent survey by the National Computer Security Association (NCSA), over 200 new viruses are created every month and close to 7,000 computer viruses have been identified worldwide (over 95% of them have been eradicated).

A computer virus functions like a biological virus, affecting a computer's underlying operating code, with results ranging from minor ailments to complete hard drive disasters. It's actually a program that duplicates itself, attaches to other programs and performs unwanted and corrupted actions within your computer.

For local area networks (LANs), viruses present an even problem. They can infect an entire network of PCs, placing valuable information and files at risk. Viruses are written primarily by mischievous programmers intent on wreaking havoc in your computer term. There are two types: the boot virus - the most common type - which prevents the user from booting up their system, and the file virus, which becomes active only when you execute a program.

AntiEXE, a common boot virus, mainly targets your system's memory and hard disk. When a computer is infected with AnitExe, the virus resides in the memory and is activated when the computer is turned on there by preventing your computer from booting up.

AntiEXE can infect diskettes when they are inserted into your computer. If you attempt to view or access the hard disk master boot sector that controls system start-up, the virus will recognize this and display pre-infected information to prevent you from discovering it. The virus can also block attempts to remove it from your computer's memory. if you try to block the virus while accessing a disk, it will overwrite parts of that disk, destroying valuable information.

"A virus may watch for a trigger event, a computer condition which causes the payload to be delivered," explains Scott Gordon, product manager with McAfee Associates, a leading virus management software company. "If a virus were to immediately harm its host, the virus would not be able to spread. Most users who uncover that they have actually been infected, have been for quite some time."

According to the NCSA, this problem will continue to as programmers become more sophisticated and creative when writing viruses. In the past year alone, the NCSA reports that an estimated 10 virus encounters per 1,000 PCs every month, and over 70% of infections occurred through diskette distribution.

Prevention is not difficult. Ultimately, it will cost you far less to buy anti-virus software than to enlist the costly services of a data recovery company. Ontrack Data Recovery of Eden Prairie, Minnesota, charges a flat rate of $200 per day in addition to a retrieval fee that can go from $200 to $1,200. "[Retrieval fees] vary depending on the severity of the problem," says Stuart Hanley, manager of engineering at Ontrack. "Other factors we have to consider are the amount of information to be retrieved and the operating system involved."

It's always a good idea to follow these safety rules:

* Use and update anti-virus software regularly. Scan newly received disks and files for viruses, including newly bought shrink-wrapped diskettes.

* To avoid a boot virus infection, don't leave floppy disks in your computer. Have a back .

* Keep the anti-virus software activated. When downloading files from the Internet, download to a disk-not your hard drive. Scan the disk before any files are put into your system.

Here are several anti-virus software programs currently available:

VirusScan supports stand-alone PCs, Novell Netware versions, DOS, OS/2 and Windows, 3.1, 95 and NT. The detection and removal data files in Virus-scan are updated every month. (See the Web site at (www:http//www.mcafee.com). List prices start at $65 to $550 for single user and network environments. McAfee Associates Santa Clara, California; 408-988-3832

Norton Anti-virus supports Windows 95, 3.1 and Netware 4.1 workstations. Upgrades can also be downloaded from the Internet via www.symantec.com. List prices start at $79.95 for stand-alone PCs to $719 for 10 user networks. Contact Symantec Corp., Cupertino, California; 408-253-9600.

Dr. So a Anti-Virus Toolkit provides an array of virus protection tools for Windows 95, 3.1, NT, Netware, Macintosh, DOS, OS/2 and UNIX users. The software lists for $125 per box and is sold only through S&S Software resellers or direct mail. The Netware version lists at $595. Updated information can also be obtained via the Internet at http://www.drsolomon.com. Contact S&S Software International in Burlington, Massachusetts, at 800-701-9648.