Viruses, pop-up ads, spyware - these are all common terms for what is now referred to as "malware". Also known as "stuff you don't want on your computer," the term is short for "malicious software". Some home computers come with good malware protection. However, do you know which anti-virus software you have installed, and whether it is still active? Do you know whether it is automatically scanning and the last time it scanned?