Keyboard loggers are tiny hardware devices that, once installed between the keyboard and keyboard input connector on a computer, grab whatever is typed into that keyboard. They don’t work on smartphones or laptops (no external keyboard) but hackers manage to find plenty of traditional PCs in hotels, financial organizations, and other public areas to exploit.
The attacker sits at the computer, acting like a normal user, to install the device. It’s easy to hide it because the keyboard cord, with keylogger installed, are usually hidden behind the computer or below it in a computer cabinet. Then the attacker leaves, waits a few days, and comes back to grab his device. With it, he takes home a gold mine of juicy passwords and other confidential information.