What is "hashcat"

Hashcat is the self-proclaimed world’s fastest CPU-based password recovery tool. It is released as free software (it had a proprietary codebase until 2015). Versions are available for Linux, OS X, and Windows and can come in CPU-based or GPU-based variants. Examples of hashcat supported hashing algorithms are Microsoft LM hashes, MD4, MD5, SHA-family, Unix Crypt formats, MySQL, Cisco PIX.

Hashcat has made its way into the news many times for the optimizations and flaws discovered by its creator, which become exploited in subsequent hashcat releases. (For example, the flaw in 1Password's hashing scheme.)