A keylogger is a device or software used to record keyboard strokes. Malicious actors may attempt to use keyloggers to record a target's username and password in order to gain unauthorized access to their accounts. Keylogging devices are a particular favorite of insider threat actors.

If a physical keylogger is being used by a criminal, they will have to place the keylogger in a computer's USB port, wait for a victim to type in their credentials, then when the victim user leaves, the criminal can retrieve the keylogger device and then see the victim's username and password. Keyloggers also come in virtual form and could be installed onto unsuspecting victims' computers via any number of means including email attachments or account takeover attacks.