Domain Objects

The STIX 2.1 specification defines a set of STIX Domain Objects (SDOs), each of which corresponds to a unique concept commonly represented in CTI. Using SDOs, STIX Cyber-observable Objects (SCOs), and STIX Relationship Objects (SROs) as building blocks, individuals can create and share broad and comprehensive cyber threat intelligence.

Property information, relationship information, and examples are provided for each SDO defined by the spec. Property information includes common properties as well as properties that are specific to each SDO. Relationship information includes embedded relationships (e.g., created_by_ref), common relationships (e.g., related-to), and SDO-specific relationships. Forward relationships (i.e., relationships from the SDO to other SDOs or SCOs) are fully defined, while reverse relationships (i.e., relationships to the SDO from other SDOs or SCOs) are duplicated for convenience.

Some SDOs are similar and can be grouped together into categories. Attack Pattern, Malware, and Tool can all be considered types of tactics, techniques, and procedures (TTPs): they describe behaviors and resources that attackers use to carry out their attacks. Similarly, Campaign, Intrusion Set, and Threat Actor all describe information about why adversaries carry out attacks and how they organize themselves.