Hashcat

Hashcat is a password recovery tool. It had a proprietary code base until 2015, but was then released as open source software. Versions are available for Linux, OS X, and Windows. Examples of hashcat-supported hashing algorithms are LM hashes, MD4, MD5, SHA-family and Unix Crypt formats as well as algorithms used in MySQL and Cisco PIX.
Hashcat has been publicly noticed because of its optimizations; partly based on flaws in other software discovered by the creator of hashcat. An example was a flaw in 1Password's password manager hashing scheme. It has also been compared to similar software in a Usenix publication and been described on Ars technica.
Variants.
Previously, two variants of hashcat existed:
With the release of hashcat v3.00, the GPU and CPU tools were merged into a single tool called hashcat. The CPU-only version became hashcat-legacy. Both CPU and GPU now require OpenCL.
Many of the algorithms supported by hashcat-legacy (such as MD5, SHA1, and others) can be cracked in a shorter time with the GPU-based hashcat. However, not all algorithms can be accelerated by GPUs. Bcrypt is an example of this. Due to factors such as data-dependent branching, serialization, and memory (and more), oclHashcat/cudaHashcat weren't catchall replacements for hashcat-legacy.
hashcat-legacy is available for Linux, OSX and Windows.
hashcat is available for macOS, Windows, and Linux with GPU, CPU and generic OpenCL support which allows for FPGAs and other accelerator cards.
Attack types.
Hashcat offers multiple attack modes for obtaining effective and complex coverage over a hash's keyspace. These modes are:
The traditional bruteforce attack is considered outdated, and the Hashcat core team recommends the Mask-Attack as a full replacement.
Competitions.
Team Hashcat (the official team of the Hashcat software composed of core Hashcat members) won first place in the KoreLogic "Crack Me If you Can" Competitions at DefCon in 2010, 2012, 2014, 2015, and 2018, and at DerbyCon in 2017.