The Bayesian Attack Model (BAM) stands as the culmination of a rigorous two-year exploration, capturing insights from 27 diverse cyber-attack instances. This model intricately chronicles the progression of a cyber-attack, subdividing it into four distinct phases: Early, Middle, Late, and Impact. Centered within BAM is the structured framework of the cyber attack process. From this core process, nodes branch out to represent the Tactics, Techniques, and Observables (TTOs) relevant to each stage. These nodes and their interconnections are grounded in historical data, highlighting the nuanced interactions between observable events and the various stages of a cyber-attack. A defining component of BAM is its Conditional Probability Tables (CPTs). Curated through intensive scrutiny of threat analysis reports and bolstered by expert elicitation sessions, these CPTs illuminate the intricate correlations between historical events and adversary techniques leveraged over years of cyber attacks. (OSTI PID No. TBD)