- Keylogger Software -
A hidden program that can be planted in the hard drive, simply saving all of the computer activities and keyboard inputs to a file that usually sent to an email that the observer entered in the keylogger installation.

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- Keylogger Hardware -
Now days there are a big verity of hardware keyloggers:
- Standard keylogger hardware (usb,ps2) -



Attached somewhere on the keyboard cable between the computer usb or ps2 ports and the keyboard, logs all keyboard inputs without depending on any programs or operating system. * Cannot be detected by any software.
- Wireless Keylogger -

One of my favorite keyloggers - it Collects packets of data being transferred from a wireless keyboard and its receiver between the two devices. Also cannot be detected by any kind of software!
- Keyboard overlays -

A keylogger overlay is fitted to look like a standard part of a hardware system. These overlays are often used at ATM terminals where the customer's PIN is recorded when the overlay is pushed along with the numbers on the ATM terminal.
- Firmware -

Very good method as well, A computer's BIOS can be reprogrammed so that it records keystrokes as it processes them. I will write a post about this method including guides and tips.