Because viruses replicate across a network in a variety of ways, they can cause Denial of Service (DoS) attacks in which the victim is not specifically targeted but is an unlucky host. Depending on the type of virus, the DoS can be hardly noticeable—or it can cause a major ­disaster.

A security expert and content editor for Symantec’s online magazine SecurityFocus notes that as of April 2005, Windows users had experienced more than 140,000 virus attacks, in contrast to the Macintosh Apple users who had experienced none. Some security experts maintain that Apple’s freedom from viruses is caused by a lack of critical mass, but Symantec’s expert thinks it is a combination of Apple’s OS X operating system and its three-tiered user-privilege system—(i) user, (ii) GUI superuser, and (iii) root—that is disabled by default. Perhaps that is why, says the Symantec security professional, that Apple experiences a 70% year-over-year growth in ­revenues.

See Also: Denial of Service (DoS); Electronic Message or Email; Root; Symantec Corporation.