Tactics for Account Access Graphs

Account access graphs have been proposed as a way to model relationships between user credentials, accounts, and methods of access; they capture both multiple simultaneous access routes (e.g., for multi-factor authentication) as well as multiple alternative access routes (e.g., for account recovery). In this paper we extend the formalism with state transitions and tactics. State transitions capture how access may change over time as users or adversaries use access routes and add or remove credentials and accounts. Tactics allow us to model and document attacker techniques or resilience strategies, by writing small programs. We illustrate these ideas using some attacks against mobile authentication and banking applications which have been publicised in 2023.