What viruses do varies but it is always bad, if sometimes amusing.

Some will try to destroy your computer (on the software level, although some will actually “physically” harm your hard drive disks). Some will simply replicate themselves, for example, sending copies of themselves to everyone in your Microsoft Outlook contact lists, then to everyone in theirs, and so on (these are called worms). Some will be programmed to create huge amounts of traffic onto certain websites – such as a major corporate site, a major commerce site or a major news outlet site – to cause the site to become unusually slow or to stop working altogether.

Some viruses are supposed to be humorous. They may make little sheep dance across your screen, or make your keyboard make belching sounds when you type.

Some viruses, often called “worms” will actually make your system misbehave in specific ways – such as redirecting your attempts to visit a certain site to another site. One famous worm recently redirected Google searches in a scheme that sent surfers to a German-based site that exactly replicated Google, except served all ads from the people sponsoring the worm!

Some viruses are not funny at all, and can destroy data that cannot be recovered. While spyware and other bad software will often need to be removed rather than prevented, viruses should be prevented, and the good news is, that’s pretty easy to do.

The most important, and luckily easiest, step any computer owner or administrator can do is to install, enable, update and continually run a quality security program that checks for viruses.

There are dozens of software brands out there but there are two that even now are head and shoulders above the rest, Norton, and McAfee.