Final answer:
The tool used to perform a credential brute force attack is John the Ripper. John the Ripper is a free and open-source password cracking tool.
Step-by-step explanation:
The tool used to perform a credential brute force attack is John the Ripper. John the Ripper is a free and open-source password cracking tool that can be used to test the strength of passwords. It works by systematically guessing different combinations of passwords until the correct one is found. The tool is commonly used by security professionals and ethical hackers to assess the vulnerability of systems and networks.