T1070.003.md

T1070.003 - Clear Command History

Description from ATT&CK

In addition to clearing system logs, an adversary may clear the command history of a compromised account to conceal the actions undertaken during an intrusion. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they've done.

On Linux and macOS, these command histories can be accessed in a few different ways. While logged in, this 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 benefit of this is that it allows users to go back to commands they've used before in different sessions.

Adversaries may delete their commands from these logs by manually clearing the history (history -c) or deleting the bash history file rm ~/.bash_history.

On Windows hosts, PowerShell has two different command history providers: the built-in history and the command history managed by the PSReadLine module. The built-in history only tracks the commands used in the current session. This command history is not available to other sessions and is deleted when the session ends.

The PSReadLine command history tracks the commands used in all PowerShell sessions and writes them to a file ($env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt by default). This history file is available to all sessions and contains all past history since the file is not deleted when the session ends.(Citation: Microsoft PowerShell Command History)

Adversaries may run the PowerShell command Clear-History to flush the entire command history from a current PowerShell session. This, however, will not delete/flush the ConsoleHost_history.txt file. Adversaries may also delete the ConsoleHost_history.txt file or edit its contents to hide PowerShell commands they have run.(Citation: Sophos PowerShell command audit)(Citation: Sophos PowerShell Command History Forensics)

Atomic Tests

• Atomic Test #1 - Clear Bash history (rm)

• Atomic Test #2 - Clear Bash history (echo)

• Atomic Test #3 - Clear Bash history (cat dev/null)

• Atomic Test #4 - Clear Bash history (ln dev/null)

• Atomic Test #5 - Clear Bash history (truncate)

• Atomic Test #6 - Clear history of a bunch of shells

• Atomic Test #7 - Clear and Disable Bash History Logging

• Atomic Test #8 - Use Space Before Command to Avoid Logging to History

• Atomic Test #9 - Disable Bash History Logging with SSH -T

• Atomic Test #10 - Prevent Powershell History Logging

• Atomic Test #11 - Clear Powershell History by Deleting History File

Atomic Test #1 - Clear Bash history (rm)

Clears bash history via rm

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

rm ~/.bash_history

Atomic Test #2 - Clear Bash history (echo)

Clears bash history via rm

Supported Platforms: Linux

Attack Commands: Run with sh!

echo "" > ~/.bash_history

Atomic Test #3 - Clear Bash history (cat dev/null)

Clears bash history via cat /dev/null

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

cat /dev/null > ~/.bash_history

Atomic Test #4 - Clear Bash history (ln dev/null)

Clears bash history via a symlink to /dev/null

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

ln -sf /dev/null ~/.bash_history

Atomic Test #5 - Clear Bash history (truncate)

Clears bash history via truncate

Supported Platforms: Linux

Attack Commands: Run with sh!

truncate -s0 ~/.bash_history

Atomic Test #6 - Clear history of a bunch of shells

Clears the history of a bunch of different shell types by setting the history size to zero

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

unset HISTFILE
export HISTFILESIZE=0
history -c

Atomic Test #7 - Clear and Disable Bash History Logging

Clears the history and disable bash history logging of the current shell and future shell sessions

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

set +o history
echo 'set +o history' >> ~/.bashrc
. ~/.bashrc
history -c

Cleanup Commands:

sed -i 's/set +o history//g' ~/.bashrc
. ~/.bashrc
set -o history

Atomic Test #8 - Use Space Before Command to Avoid Logging to History

Using a space before a command causes the command to not be logged in the Bash History file

Supported Platforms: Linux, macOS

Attack Commands: Run with sh!

hostname
whoami

Atomic Test #9 - Disable Bash History Logging with SSH -T

Keeps history clear and stays out of lastlog,wtmp,btmp ssh -T keeps the ssh client from catching a proper TTY, which is what usually gets logged on lastlog

Supported Platforms: Linux

Attack Commands: Run with sh!

sshpass -p 'pwd101!' ssh testuser1@localhost -T hostname

Cleanup Commands:

userdel -f testuser1

Dependencies: Run with sh!

Description: Install sshpass and create user account used for excuting

Check Prereq Commands:

/usr/sbin/useradd testuser1
echo pwd101! | passwd testuser1 --stdin 

Get Prereq Commands:

yum -y install epel-release
yum -y install sshpass

Atomic Test #10 - Prevent Powershell History Logging

Prevents Powershell history

Supported Platforms: Windows

Attack Commands: Run with powershell!

Set-PSReadlineOption –HistorySaveStyle SaveNothing

Cleanup Commands:

Set-PSReadLineOption -HistorySaveStyle SaveIncrementally

Atomic Test #11 - Clear Powershell History by Deleting History File

Clears Powershell history

Supported Platforms: Windows

Attack Commands: Run with powershell!

Remove-Item (Get-PSReadlineOption).HistorySavePath