Macro viruses were discovered in July 1995 and are the most common and rapidly growing viruses ever recorded. The 1997 Virus Prevalence Survey of the National Computer Security Association revealed that macro viruses accounted for 80 percent of all virus attacks in the corporations surveyed. The newsletter Virus Bulletin listed 530 macro viruses in its April 1997 report. Antivirus program developers have made great strides in building protections into widely used operating systems, but these systems do poorly in protecting against macro viruses. Network managers generally use a combination of policy and antivirus scanning products to combat viruses. No solution will ever provide 100 percent protection. However, companies can help prevent data destruction by keeping up with the latest attacks and detection methods and revising their in-house procedures accordingly.