As the name implies, this is software that "spies" on your computer. Nobody likes to be spied on, and your computer doesn't like it either. Spyware can capture information like Web browsing habits, e-mail messages, usernames and passwords, and credit card information. If left unchecked, the software can transmit this data to another person's computer over the Internet.
So how does spyware get on your computer? Just like viruses, spyware can be installed when you open an e-mail attachment containing the malicious software. It can also be installed when you install another program that has a spyware installer attached to it. Because of the insidious nature of spyware, most people don't even know when spyware is on their computer. Fortunately, you can purchase anti-spyware utilities that will search for spyware on your computer and stomp the unwanted software out of your system. A good way to prevent spyware from infecting your computer is to install a security program that lets you know when any program is being installed, so that you can choose to authorize or stop the installation.