Keylogger A keylogger is a program or hardware device that records every keystroke. Software keyloggers run covertly in the background, while hardware variants can be physically attached between the keyboard and the computer.

Rootkit A rootkit is hard to see, and that is its most important property. It can settle beneath the operating system and beneath the layer where antivirus software can look: sometimes in drivers or in the kernel, out of reach of protective mechanisms, sometimes in the boot phase, even in the motherboard firmware. From there it hides itself and everything else the attacker does, so an infected system looks perfectly clean.