Spyware

Spyware is a term coined to describe computer program code written with the intent to monitor and gather data about computer users and their operations and then to report back to a specified server. In some instances, data is analyzed for frequently accessed web sites leading the server to send the computer user's internet browser, pop-up windows of related advertising pages. What may have appeared to be a helpful at some point in history has turned out to be a major source of annoyance, aggravation and disreputable if not illegal activity. Wikipedia provides an article outlining the emergence of the term and discusses many of the issues surrounding the use of spyware. Please read the article entitled"Spyware".

Computer performance:

According to the Wikipedia article, there are many spyware programs on the web and a single computer may accumulate more than one causing substantial loss of system performance. If your computer takes a long time to load programs and to access files; if your computer crashes a lot and seems to hang (stops processing key presses or mouse clicks); if while browsing the internet, unsolicited windows with advertising frequently appear; then one or many spyware programs could be stealing your computer processing resources.

Once again, just like for viruses, there are many commercially available and free programs which claim to erase spy programs from the computer system. Care must be taken with the free programs to download them from a reliable and trusted source as unscrupulous software authors have written code pretending to remove spyware but really performing an install of spyware instead.