Software and hardware, created for the sole purpose of monitoring computer activity, have become common and popular. Unfortunately, software and hardware of this kind, if misused, are also capable of stealing information. One of the most effective ways of stealing information from a PC is capturing keystrokes. It would not be out of place to know the enemy better. Well, here they are:

Keylogging Programs (keyloggers, key loggers, keystroke loggers, key recorders, key trappers, key capture programs, etc.) belong to the group of tools that monitor PC activity. A small, fairly simple program (a programmer can write a plain one in a couple of days) captures everything the user is doing - keystrokes, mouse clicks, files opened and closed, sites visited. A little more sophisticated programs of this kind also capture text from windows and make screenshots (record everything displayed on the screen) - so the information is captured even if the user doesn't type anything, just opens the views the file.
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Hardware keyloggers (Keylogging hardware devices, keystroke recording devices, etc.) are pretty small; an average hardware keylogger is about half a size of a lighter. They easily can be attached between a keyboard and a computer, disguised as a some computer gadget. Other models are built into the keyboard itself, which makes them almost impossible to detect.
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Keylogging programs and devices have become a serious threat to the security of information stored on PCs.

Actually, the technologies applied in monitoring software and hardware are dual-purpose ones. These tools can be useful indeed - if applied right. Large and middle-sized companies use legitimate monitoring programs and hardware devices for workplace surveillance to ensure information security and local network accountability. Law enforcement agencies may also use keystroke loggers to gather evidence on suspected criminals. At home more and more parents use them as a "life jacket" for their web-surfing kids.

On the other hand, keylogging programs and devices can be (and, in fact, often are) used illicitly - from simply spying on a spouse to committing cybercrimes as serious as identity theft and espionage.