Find sigma rule 
Attack: Input Capture: Keylogging
Adversaries may log user keystrokes to intercept credentials as the user types them. Keylogging is likely to be used to acquire credentials for new access opportunities when OS Credential Dumping efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured. In order to increase the likelihood of capturing credentials quickly, an adversary may also perform actions such as clearing browser cookies to force users to reauthenticate to systems.(Citation: Talos Kimsuky Nov 2021)
Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes.(Citation: Adventures of a Keystroke) Some methods include:
- Hooking API callbacks used for processing keystrokes. Unlike Credential API Hooking, this focuses solely on API functions intended for processing keystroke data.
- Reading raw keystroke data from the hardware buffer.
- Windows Registry modifications.
- Custom drivers.
- Modify System Image may provide adversaries with hooks into the operating system of network devices to read raw keystrokes for login sessions.(Citation: Cisco Blog Legacy Device Attacks)
MITRE
Tactic
- credential-access
- collection
technique
- T1056.001
Test : Bash session based keylogger
OS
- linux
Description:
When a command is executed in bash, the BASH_COMMAND variable contains that command. For example :~$ echo $BASH_COMMAND = “echo $BASH_COMMAND”. The trap command is not a external command, but a built-in function of bash and can be used in a script to run a bash function when some event occurs. trap will detect when the BASH_COMMAND variable value changes and then pipe that value into a file, creating a bash session based keylogger.
To gain persistence the command could be added to the users .bashrc or .bash_aliases or the systems default .bashrc in /etc/skel/
Executor
bash