Query: SIEM correlation: defense impairment activity consistent with Prevent Command History Logging
Matching passage: T1690 Prevent Command History Logging. Tactics: defense impairment. Description: Adversaries may impair command history logging to hide commands they run on a compromised system. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they have done. On Linux and macOS, command history is tracked in a file pointed to by the environment variable `HISTFILE`. When a user logs off a system, this information is flushed to a file in the user's home directory called `~/.bash_history`. The `HISTCONTROL` environment variable keeps track of what should be saved by the history command and eventually into the `~/.bash_history` file when a user logs out. `HISTCONTROL` does not exist by default on macOS, but can be set by the user and will be respected. The `HISTFILE` environment variable is also used in some ESXi systems.(Citation: Google Cloud Threat Intelligence ESXi VIBs 2022) Adversaries may clear the history environment variable (`unset HISTFILE`) or set the command history size to zero (`export HISTFILESIZE=0`) to prevent logging of commands. Additionally, `HISTCONTROL` can be configured to ignore commands that start with a space by simply setting it to "ignorespace". `HISTCONTROL` can also be set to ignore duplicate commands by setting it to "ignoredups". In some Linux systems, this is set by default to "ignoreboth" which covers both of the previous examples. This means that " ls" will not be saved, but "ls" would be saved by history. Adversaries can abuse this to operate without leaving traces by simply prepending a space to all of their terminal commands. On Windows systems, the `PSReadLine` module tracks commands used in all PowerShell sessions and writes them to a file (`$env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt` by default). Adversaries may change where these logs are saved using `Set-PSReadLineOption -HistorySavePath {File Path}`. This will cause `ConsoleHost_history.txt` to stop receiving logs. Additionally, it is possible to turn off logging to this
Near-miss passage: T1686.003 Windows Host Firewall. Tactics: defense impairment. Description: Adversaries may disable or modify the Windows host firewall to bypass controls limiting network usage. This can include disabling the Windows host firewall entirely, suppressing specific profiles (domain, private, public), or adding, deleting, and modifying firewall rules to allow or restrict traffic.(Citation: Nearest Neighbor Volexity) Adversaries may perform these modifications through multiple mechanisms depending on the Windows operating system and access level. For example, adversaries may use command-line utilities (e.g., `netsh advfirewall` or PowerShell cmdlets like `Set-NetFirewallProfile`, `New-NetFirewallRule`), Windows Registry modifications (e.g., altering firewall states and rule configurations via registry keys), or the Windows Control Panel to modify firewall settings through the Windows Security interface. By disabling or modifying Windows firewall services, adversaries may enable access to remote services, open ports for command and control traffic, or configure rules for further actions.