Attack Index is intended to quantify user-centric risk by combining the severity of threats a user is exposed to and the diversity of those threats over time (D). This aligns with how IR prioritizes investigations: a user repeatedly targeted by multiple high-severity threat types (credential phishing + impostor/BEC + malware delivery) represents a higher likelihood of compromise and greater operational risk than a user receiving large volumes of low-risk spam. In Proofpoint SOC workflows, Attack Index helps drive proactive actions---focus investigations on ''most attacked'' users, increase monitoring, enforce stronger controls (MFA, conditional access), and deliver targeted training interventions for users with risky behavior. VIP status can be used for business-impact prioritization, but it is not the defining calculation factor for ''threat burden.'' Active Directory group membership may be used for segmentation and reporting but is not the core metric component. The concept is to score what the user is facing in terms of threat intensity and breadth, enabling triage on the People page and supporting escalation decisions when high Attack Index correlates with clicks or delivered accessible threats.