Which of the following tools is categorized as spyware?

A keylogger is classified as spyware because it is designed to covertly monitor and capture the keystrokes of a user, thereby gathering sensitive information such as passwords, credit card numbers, and personal correspondence without the user's consent. This behavior aligns with the primary objective of spyware, which is to collect personal or sensitive data under the guise of legitimate functionality.

Unlike a keylogger, a firewall is a security tool that controls incoming and outgoing network traffic based on predetermined security rules. Antivirus software is designed to detect, prevent, and remove malware, functioning as a protective measure against various types of attacks rather than as a means of covertly monitoring user behavior. Meanwhile, data encryption tools serve to secure information by converting it into a coded format, thus protecting the data from unauthorized access rather than capturing it. Therefore, the defining characteristic of spyware is its capacity to stealthily gather user data, which is primarily exhibited by keyloggers.