What is Mimikatz?
Mimikatz, described by the author as just "a little tool to play with Windows security," is an incredibly effective offensive security tool developed by Benjamin Delpy. It is used by penetration testers and malware authors alike. The destructive 2017 NotPetya malware rolled leaked NSA exploits like EternalBlue together with Mimikatz to achieve maximum damage.
Originally conceived as a research project by Delpy to better understand Windows security, Mimikatz also includes a module that dumps Minesweeper from memory and tells you where all the mines are located.
Mimikatz is not difficult to use, and Mimikatz v1 comes bundled as a meterpreter script as part of Metasploit. The new Mimikatz v2 upgrade has not yet been integrated into Metasploit as of this writing.
The name "mimikatz" comes from the French slang "mini" meaning cute, thus "cute cats." (Delpy is French and he blogs on Mimikatz in his native language.)