CrackMapExec (a.k.a CME) is a post-exploitation tool that helps automate assessing the security of large Active Directory networks. Built with stealth in mind, CME follows the concept of "Living off the Land": abusing built-in Active Directory features/protocols to achieve it's functionality and allowing it to evade most endpoint protection/IDS/IPS solutions.
CME makes heavy use of the Impacket library (developed by @asolino) for working with network protocols and performing a variety of post-exploitation techniques.
Although meant to be used primarily for offensive purposes (e.g. red teams, internal pentest), CME can be used by blue teams as well to assess account privileges, find possible misconfigurations and simulate attack scenarios.