A program that has the ability to scan and/or monitor your computer, then relays the information over cyber-space. Among the information that may be actively or passively gathered is: passwords, log-in details, account numbers, personal information, individual files or other personal documents. Spyware may also gather and distribute information related to the user's computer, applications running on the computer, Internet browser usage or other computing habits.

Spyware frequently attempts to remain unnoticed, either by actively hiding or by simply not making its presence on a system known to the user. Spyware can be downloaded from Web sites (typically in shareware or freeware), email messages, and instant messengers. Additionally, a user may unknowingly receive and/or trigger spyware by accepting an End User License Agreement from a software program linked to the spyware or from visiting a website that downloads the spyware with or without an End User License Agreement.