Hardware keylogger
Hardware keyloggers are used for keystroke logging, a method of capturing and recording computer users' keystrokes, including sensitive passwords. They can be implemented via BIOS-level firmware, or alternatively, via a device plugged inline between a computer keyboard and a computer. They log all keyboard activity to their internal memory. Description. Hardware keyloggers have an advantage over software keyloggers as they can begin logging from the moment a computer is turned on (and are therefore able to intercept passwords for the BIOS or disk encryption software). All hardware keylogger devices have to have the following: Generally, recorded data  is retrieved by typing a special password into a computer text editor. The hardware keylogger plugged in between the keyboard and computer detects that the password has been typed and then presents the computer with "typed" data to produce a menu. Beyond text menu some keyloggers offer a high-speed download to speed up retrieval of stored data; this can be via USB mass-storage enumeration or with a USB or serial download adapter. Typically the memory capacity of a hardware keylogger may range from a few kilobytes to several gigabytes, with each keystroke recorded typically consuming a byte of  memory. Countermeasures. Denial or monitoring of physical access to sensitive computers, e.g. by closed-circuit video surveillance and access control, is the most effective means of preventing hardware keylogger installation. Visual inspection is the easiest way of detecting hardware keyloggers. But there are also some techniques that can be used for most hardware keyloggers on the market, to detect them via software. In cases in which the computer case is hidden from view (e.g. at some public access kiosks where the case is in a locked box and only a monitor, keyboard, and mouse are exposed to view) and the  user has no possibility to run software checks, a user might thwart a keylogger by typing part of a password, using the mouse to move to a text editor or other window, typing some garbage text, mousing back to the password window, typing the next part of the password, etc. so that the keylogger will record an unintelligible mix of garbage and password text. General "keystroke logging countermeasures" are also options against hardware keyloggers. The main risk associated with keylogger use is that physical access is needed twice: initially to install the keylogger, and secondly to retrieve it. Thus, if  the victim discovers the keylogger, they can then set up a sting operation to catch the person in the act of retrieving it. This could include camera surveillance or the review of access card swipe records to determine who gained physical access to the area during the time period that the keylogger was removed.