Spyware

Software that is secretly or surreptitiously installed into an information system without the knowledge of the system user or owner.

Software whose purpose is to monitor a computer user’s actions (e.g., web sites visited) and report these actions to a third party, without the informed consent of that machine’s owner or legitimate user Scope Note: A particularly malicious form of spyware is software that monitors keystrokes to obtain passwords or otherwise gathers sensitive information such as credit card numbers, which it then transmits to a malicious third party. The term has also come to refer more broadly to software that subverts the computer’s operation for the benefit of a third party.

computer software that obtains information from a user's computer without the user's knowledge or consent