Spyware

Spyware is a type of malicious software that collects information on a user without their knowledge, typically sending it to a third party, or directing ads to the user's computer without permission.

Unlike viruses and worms, spyware is not self-replicating, and thus does not spread from one infected machine to another.  It does, however, allow the author of the spyware to exploit the infected machine in a number of ways:

• Directing pop-up ads to the user
• Redirecting the browser to advertising or malware-infected sites
• Stealing usernames and passwords from legitimate websites
• Stealing credit card and other financial details

You can minimize spyware infections in two ways:

First, know what you are installing. If a pop-up window requests permission to install software and you did not request to install, cancel the operation.

Second, install an antispyware solution; there are several inexpensive and even free options available from trusted companies.