You’re probably familiar with viruses, as they have been around the longest and most people are familiar with “virus software,” more accurately termed virus detection and removal software.

A computer virus is normally an executable program that arrives on your computer hidden within something else, like an email, or an email attachment. The typical computer virus is designed, very simply, to cause you, your computer, and other computers, problems.

You may wonder why anyone would bother to develop software specifically to cause problems, and the motives are as complex as the motives for any bad behavior. Some viruses have been developed by programmers to see what could accomplish, in a mischievous way.

Some have been developed to hurt certain companies or industries by, for example, aggrieved ex employees or nefarious competitors. Some have been developed for political or other purposes – including, debatably, actual terrorism, since “denial of service” and other virus-based online attacks can make communications stop for a while.

We’re more concerned with what they do and how to stop them than why people bother to invent and disseminate them in the first place.