Kernel

The term kernel refers to the core of an operating system that supports all other operations. By contrast, the term shell is used to describe the user interface.

Keylogger

Used by a third-party to obtain confidential data (login details, passwords, credit card numbers, PINs, etc.) by intercepting key presses. Backdoor Trojans typically come with a built-in keylogger; and the confidential data is relayed to a remote cybercriminal to be used to make money illegally or gain unauthorized access to a network or other resource.