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).[1] On ESXi servers, command history may be manually removed from the /var/log/shell.log file.[2]
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.[3]
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.[4][5]
| ID | Name | Description |
|---|---|---|
| G0096 | APT41 |
APT41 attempted to remove evidence of some of its activity by deleting Bash histories.[6] |
| G1023 | APT5 |
APT5 has cleared the command history on targeted ESXi servers.[7] |
| G0143 | Aquatic Panda |
Aquatic Panda cleared command history in Linux environments to remove traces of activity after operations.[8] |
| S0601 | Hildegard |
Hildegard has used history -c to clear script shell logs.[9] |
| S1203 | J-magic |
J-magic can overwrite previously executed command line arguments.[10] |
| S0641 | Kobalos |
Kobalos can remove all command history on compromised hosts.[11] |
| G0032 | Lazarus Group |
Lazarus Group has routinely deleted log files on a compromised router, including automatic log deletion through the use of the logrotate utility.[12] |
| G0059 | Magic Hound |
Magic Hound has removed mailbox export requests from compromised Exchange servers.[13] |
| G1051 | Medusa Group |
Medusa Group has cleared command history by running the PowerShell command |
| G0045 | menuPass |
menuPass has used Wevtutil to remove PowerShell execution logs.[15] |
| G0139 | TeamTNT |
TeamTNT has cleared command history with |
| ID | Mitigation | Description |
|---|---|---|
| M1039 | Environment Variable Permissions |
Making the environment variables associated with command history read only may ensure that the history is preserved.[18] |
| M1029 | Remote Data Storage |
Forward logging of historical data to remote data store and centralized logging solution to preserve historical command line log data. |
| M1022 | Restrict File and Directory Permissions |
Preventing users from deleting or writing to certain files can stop adversaries from maliciously altering their |
| ID | Name | Analytic ID | Analytic Description |
|---|---|---|---|
| DET0165 | Behavioral Detection of Command History Clearing | AN0467 |
Detects adversary behavior clearing command history via |
| AN0468 |
Detects adversary clearing shell history using |
||
| AN0469 |
Detects PowerShell |
||
| AN0470 |
Detects modification or truncation of |
||
| AN0471 |
Detects use of |