Keystroke logging (often calle keylogging) is a method of capturing and recording user keystrokes. Keylogging can be useful to determine sources of errors in computer systems, to study how users interact and access with systems, and is sometimes used to measure employee productivity on certain clerical tasks. Such systems are also highly useful for law enforcement and espionage—for instance, providing a means to obtain passwords or encryption keys and thus bypassing other security measures. Keyloggers are widely available on the Internet.