Networking-Dojo

How to Generate YARA Rules with YarGen

This guide provides a straightforward method for creating YARA rules from malware samples using YarGen and MalwareBazaar.

1. Setup Your Environment

CRITICAL: Before you start, use a completely isolated virtual machine (VM). Do not handle malware on a machine connected to your network or containing sensitive data.

Inside your VM, open a terminal and follow these steps:

  • Clone the repository
  • Create and activate a Python virtual environment(Note: Use source venv/bin/activate on Linux/macOS)
  • Install required packages
  • Update the YarGen signature database: This helps reduce false positives.
git clone https://github.com/Neo23x0/yarGen.gitcd yarGen
python3.10 -m venv
venv venv\Scripts\activate
pip install -r requirements.txt
python yarGen.py --update

2. Download a Malware Sample

  • In your isolated VM, go to https://bazaar.abuse.ch/browse/.
  • Download a malware sample to analyze.

3. Generate the YARA Rule

  • Navigate back to your terminal running in the yarGen directory.
  • Run the following command, pointing it to your downloaded malware file
python yarGen.py -m [PATH_TO_YOUR_MALWARE_FILE]

4. Review the Output

YarGen will process the file and generate YARA rules based on the strings it finds.

The output is saved in yargen_rules.yar, containing the generated rule.

The tool extracts unique strings from the malware to create detection logic. This automates a significant part of the rule-writing process.

The strings section of the rule shows the specific indicators YarGen identified in the malware sample.

By

Sam Tanner