Is my computer infected with spyware, adware, or a virus or trojan?

Very generally, the computer behaving in an unexpected manner is an indicator that there is the possibility of a malware infection of some sort. Almost every unprotected machine will have some 'low-level' spyware present such as undesirable tracking cookies. There is no need to be alarmed with this, however. Low level infections are easily treated with regular scans with recently updated anti-virus and anti-spyware scanners.

More specifically, the presence of spyware, adware or a virus or trojan on your computer will usually include one or more of the following symptoms:

• your computer is running more slowly than usual (often painfully so)
• you are experiencing regular program or system crashes
• you are plagued with popup windows or numerous browser windows opening automatically
• you have unusual entries in your browser toolbar
• your Internet home page has changed
• clicking on links has unexpected and unrelated results
• there are unexplained entries in your Internet favorites
• unexplained icons appear on your desktop
• your browser closes unexpectedly
• you notice some programs on the computer you don’t remember installing
• your Internet connection is painfully slow or you are receiving many “This page cannot be displayed” error pages in your browser
• your Internet usage fees have skyrocketed but you’re not doing much more on the Internet than usual
• you are receiving phone bills with unusual, unexplained and / or expensive entries
• you are receiving an unusually high number of bounced emails and / or complaints that you are emailing viruses to people
• your computer keeps re- starting on its own
• the amount of SPAM emails suddenly and dramatically increases
  

Of course, some of these symptoms may have other causes, such as hardware failure or a different user making changes to the system.

It is a fact that most computers with an internet connection will have some form of malware active on them. Even heavily protected corporate systems are vulnerable to malware installation.