Hydra: Exceeding 4 Billion Passwords

TL;DR

Hydra’s default configuration limits password checking to around 4 billion combinations. This guide explains how to modify Hydra’s settings and use alternative methods (like wordlists with masks) to bypass this limit and test a larger password space.

Solution Guide

1. Understand the Limit: Hydra’s limitation stems from its internal representation of passwords as 32-bit integers. This allows for approximately 4,294,967,296 (2³²) unique combinations.
2. Modify Hydra Configuration Files: The core solution involves changing how Hydra handles password generation and checking.
   • Disable Password Filtering: By default, Hydra filters out passwords that don’t meet certain criteria. Disabling this can allow more combinations to be tested. Edit your Hydra configuration file (often located in /etc/hydra/hydra.conf or a custom config) and comment out or remove lines related to password filtering.
   • Increase Max Combinations (If Possible): Some Hydra versions might have an option to directly increase the maximum number of combinations. Check your configuration file for settings like max_combinations or similar. However, this isn’t always effective due to underlying limitations.
3. Utilize Wordlists with Masks: This is the most reliable method.
   • Create a Large Wordlist: Generate a wordlist containing potential passwords. The larger the list, the more combinations you can test. Tools like crunch or custom scripts can help create these lists.
   • Use Masks to Expand Combinations: Masks allow Hydra to systematically modify parts of your wordlist, creating many variations.

     hydra -l username -P /path/to/wordlist ?d?d?d?d?d?d target_service
     

     In this example, ?d represents a digit (0-9). The mask ?d?d?d?d?d?d will create variations by changing each of the six digits.

   • Combine Wordlists and Masks: You can combine wordlists with masks to test even more combinations.

     hydra -l username -P /path/to/wordlist1,/path/to/wordlist2 ?d?d target_service
     

4. Split the Wordlist: For extremely large wordlists, split them into smaller files.
   • Use a tool like csplit to divide your wordlist.
   • Run Hydra in parallel on each file using multiple instances or a script.

     for i in {1..10}; do hydra -l username -P /path/to/wordlist_$i target_service &; done
     

5. Consider Alternative Tools: If Hydra continues to struggle, explore other password cracking tools like Hashcat or John the Ripper. These often have better support for large wordlists and more advanced features.
6. Resource Considerations: Testing billions of passwords requires significant computational resources (CPU, memory, disk I/O). Ensure your system can handle the load. Slow performance may indicate resource limitations.