_“MITRE ATT&CK® is a globally-accessible knowledge base of adversary tactics and techniques (TTTs) based on real-world observations. The ATT&CK knowledge base is used as a foundation for the development of specific threat models and methodologies in the private sector, in government, and in the cybersecurity product and service community.”_
https://attack.mitre.org/
A knowledge base for describing the behavior of adversaries.