Reviewing BPMN as a Modeling Notation for CACAO Security Playbooks

As cyber systems become increasingly complex and cybersecurity threats become more prominent, defenders must prepare, coordinate, automate, document, and share their response methodologies to the extent possible. The CACAO standard was developed to satisfy the above requirements providing a common machine-readable framework and schema to document cybersecurity operations processes, including defensive tradecraft and tactics, techniques, and procedures. Although this approach is compelling, a remaining limitation is that CACAO provides no native modeling notation for graphically representing playbooks, which is crucial for simplifying their creation, modification, and understanding. In contrast, the industry is familiar with BPMN, a standards-based modeling notation for business processes that has also found its place in representing cybersecurity processes. This research examines BPMN and CACAO and explores the feasibility of using the BPMN modeling notation to graphically represent CACAO security playbooks. The results indicate that mapping CACAO and BPMN is attainable at an abstract level; however, conversion from one encoding to another introduces a degree of complexity due to the multiple ways CACAO constructs can be represented in BPMN and the extensions required in BPMN to fully support CACAO.