This document discusses keyloggers, which are programs or hardware devices that record keyboard input without the user's consent. It describes how keyloggers can be used to monitor employee productivity or for law enforcement but can also enable illegal surveillance. Keyloggers can be installed as hardware devices attached between the keyboard and computer or as software that runs covertly in the background. The document provides examples of specific hardware and software keylogger programs and notes some methods of defending against keylogger surveillance, such as keeping systems updated with antivirus software.