Unpacking Pyarmor v8+ Scripts: Analyzing a Malware Campaign

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2025-02-13

In a recent collaboration, my colleague Leonard Rapp and I analyzed a sophisticated malware campaign that utilized Pyarmor v8+ to obfuscate its payloads. Pyarmor is a tool often used to protect Python scripts, but in this case, it was weaponized to deliver malicious code. Our findings are detailed in the blog post on our company’s website: cyber.wtf.

Key Insights and Analysis

The malware campaign involved multiple stages, starting with the delivery of a Pyarmor-obfuscated script. Pyarmor v8+ introduces advanced obfuscation techniques, making it challenging to reverse-engineer the payload. Here’s a breakdown of our analysis:

  1. Initial Payload Delivery: The malware was distributed via phishing emails containing malicious attachments. Once executed, the script used Pyarmor to load additional modules.
  2. Obfuscation Techniques: Pyarmor v8+ employs string encryption, code splicing, and dynamic loading to evade detection. We used dynamic analysis tools to deobfuscate the script.
  3. Command and Control (C2) Communication: The malware established communication with a remote server to download additional payloads and exfiltrate data.

Practical Commands and Tools Used

To analyze the malware, we utilized the following tools and commands:

  • Dynamic Analysis with GDB:
    gdb -q ./malware_sample
break main
run
disassemble

    This allowed us to inspect the binary’s execution flow.

  • Python Deobfuscation:

    import pyarmor_unpack
pyarmor_unpack.unpack('obfuscated_script.py')

This script helped us reverse-engineer the Pyarmor-protected code.

  • Network Traffic Analysis with Wireshark:

    wireshark -k -i eth0 -f "host <C2_IP>"

    We captured and analyzed network traffic to identify C2 communication.

  • YARA Rules for Detection:

    rule Pyarmor_Malware {
meta:
description = "Detects Pyarmor-obfuscated malware"
strings:
$pyarmor = "Pyarmor" nocase
condition:
$pyarmor
}

    This YARA rule was used to detect similar malware samples.

What Undercode Say

The analysis of this Pyarmor-based malware campaign highlights the evolving sophistication of cyber threats. Attackers are increasingly leveraging legitimate tools like Pyarmor to bypass security measures. To defend against such threats, cybersecurity professionals must adopt a multi-layered approach:

  1. Behavioral Analysis: Use tools like Cuckoo Sandbox to monitor the behavior of suspicious scripts.
  2. Deobfuscation Techniques: Familiarize yourself with tools like `uncompyle6` and `pyarmor_unpack` to reverse-engineer obfuscated code.
  3. Network Monitoring: Implement robust network monitoring solutions to detect and block C2 communications.
  4. Threat Intelligence: Stay updated on emerging threats by following cybersecurity blogs like cyber.wtf.

Additionally, here are some Linux and Windows commands to enhance your cybersecurity practices:

  • Linux:
    </li>
</ul>

<h1>Monitor running processes</h1>

ps aux | grep suspicious_process

<h1>Check open network connections</h1>

netstat -tuln

<h1>Analyze system logs</h1>

tail -f /var/log/syslog
    • Windows:
      </li>
</ul>

<h1>List active processes</h1>

Get-Process

<h1>Check network connections</h1>

netstat -ano

<h1>Analyze event logs</h1>

Get-WinEvent -LogName Security

      By combining these tools and techniques, you can better defend against advanced malware campaigns. For further reading, visit cyber.wtf to explore our detailed analysis. Stay vigilant and keep your systems secure!

      References:

      Hackers Feeds, Undercode AIFeatured Image

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