T1070.003
Indicator Removal on Host: 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.
Adversaries may also leverage a Network Device CLI on network devices to clear command history data (clear logging and/or clear history).(Citation: US-CERT-TA18-106A)
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)
Clears bash history via rm
Supported Platforms: linux,macos
auto_generated_guid: a934276e-2be5-4a36-93fd-98adbb5bd4fc
Inputs:
None
Attack Commands: Run with sh!
1
2
rm ~/.bash_history
Atomic Test #2 - Clear Bash history (echo)
Clears bash history via rm
Supported Platforms: linux
auto_generated_guid: cbf506a5-dd78-43e5-be7e-a46b7c7a0a11
Inputs:
None
Attack Commands: Run with sh!
1
2
echo "" > ~/.bash_history
Atomic Test #3 - Clear Bash history (cat dev/null)
Clears bash history via cat /dev/null
Supported Platforms: linux,macos
auto_generated_guid: b1251c35-dcd3-4ea1-86da-36d27b54f31f
Inputs:
None
Attack Commands: Run with sh!
1
2
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
auto_generated_guid: 23d348f3-cc5c-4ba9-bd0a-ae09069f0914
Inputs:
None
Attack Commands: Run with sh!
1
2
ln -sf /dev/null ~/.bash_history
Atomic Test #5 - Clear Bash history (truncate)
Clears bash history via truncate
Supported Platforms: linux
auto_generated_guid: 47966a1d-df4f-4078-af65-db6d9aa20739
Inputs:
None
Attack Commands: Run with sh!
1
2
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
auto_generated_guid: 7e6721df-5f08-4370-9255-f06d8a77af4c
Inputs:
None
Attack Commands: Run with sh!
1
2
3
4
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
auto_generated_guid: 784e4011-bd1a-4ecd-a63a-8feb278512e6
Inputs:
None
Attack Commands: Run with sh!
1
2
3
4
5
set +o history
echo 'set +o history' >> ~/.bashrc
. ~/.bashrc
history -c
Cleanup Commands:
1
2
3
4
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
auto_generated_guid: 53b03a54-4529-4992-852d-a00b4b7215a6
Inputs:
None
Attack Commands: Run with sh!
1
2
3
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
auto_generated_guid: 5f8abd62-f615-43c5-b6be-f780f25790a1
Inputs:
None
Attack Commands: Run with sh!
1
2
sshpass -p 'pwd101!' ssh testuser1@localhost -T hostname
Cleanup Commands:
1
2
userdel -f testuser1
Dependencies: Run with sh!
Description: Install sshpass and create user account used for excuting
Check Prereq Commands:
1
2
$(getent passwd testuser1 >/dev/null) && $(which sshpass >/dev/null)
Get Prereq Commands:
1
2
3
4
/usr/sbin/useradd testuser1
echo -e 'pwd101!\npwd101!' | passwd testuser1
(which yum && yum -y install epel-release sshpass)||(which apt-get && DEBIAN_FRONTEND=noninteractive apt-get install -y sshpass)
Atomic Test #10 - Prevent Powershell History Logging
Prevents Powershell history
Supported Platforms: windows
auto_generated_guid: 2f898b81-3e97-4abb-bc3f-a95138988370
Inputs:
None
Attack Commands: Run with powershell!
1
2
Set-PSReadlineOption -HistorySaveStyle SaveNothing
Cleanup Commands:
1
Set-PSReadLineOption -HistorySaveStyle SaveIncrementally
Atomic Test #11 - Clear Powershell History by Deleting History File
Clears Powershell history
Supported Platforms: windows
auto_generated_guid: da75ae8d-26d6-4483-b0fe-700e4df4f037
Inputs:
None
Attack Commands: Run with powershell!
1
2
Remove-Item (Get-PSReadlineOption).HistorySavePath
Atomic Test #12 - Set Custom AddToHistoryHandler to Avoid History File Logging
The "AddToHistoryHandler" receives the current command as the $line variable and then returns $true if the line should be written to the history file. Here we simply return $false so nothing gets added to the history file for the current session.
Supported Platforms: windows
auto_generated_guid: 1d0d9aa6-6111-4f89-927b-53e8afae7f94
Inputs:
None
Attack Commands: Run with powershell!
1
2
Set-PSReadLineOption -AddToHistoryHandler { return $false }
Cleanup Commands:
1
2
Set-PSReadLineOption -AddToHistoryHandler $null