Experts have identified about 500 computer viruses--computer codes that can cause PCs to go haywire. There are programs to immunize PCs against known viruses, but new strains, against which PC owners are unprotected, appear every week. Software maker XTree Co. in San Luis Obispo, Calif., says it can help.
The latest version of its ViruSafe package has a data base of all known viruses. From that, the program can eliminate recognized viruses residing in a PC's memory or hard drive and spot suspicious-looking codes that could be a new virus. To determine if a code is indeed a virus, ViruSafe creates a temporary file and monitors what the code does to it. If it proves harmful to the test file, ViruSafe adds the new virus to its data base and removes the alien program from the PC. ViruSafe, itself, is also intended to be immune: It is composed of six overlapping modules, so if the program becomes infected, the damaged portion is deleted and rebuilt from the unaffected five automatically.