Policy mining is an automated procedure for generating access rules by means of mining patterns from single permissions, which are typically registered in access logs. Attribute-based access control (ABAC) is a model which allows security administrators to create a set of rules, known as the access control policy, to restrict access in information systems by means of logical expressions defined through the attribute–values of three types of entities: users, resources, and environmental conditions. The application of policy mining in large-scale systems oriented towards ABAC is a must because it is not workable to create rules by hand when the system requires the management of thousands of users and resources. In the literature on ABAC policy mining, current solutions follow a frequency-based strategy to extract rules; the problem with that approach is that selecting a high-frequency support leaves many resources without rules (especially those with few requesters), and a low support leads to the rule explosion of unreliable rules. Another challenge is the difficulty of collecting a set of test examples for correctness evaluation, since the classes of user–resource pairs available in logs are imbalanced. Moreover, alternative evaluation criteria for correctness, such as peculiarity and diversity, have not been explored for ABAC policy mining. To address these challenges, we propose the modeling of access logs as affiliation networks for applying network and biclique analysis techniques (1) to extract ABAC rules supported by graph patterns without a frequency threshold, (2) to generate synthetic examples for correctness evaluation, and (3) to create alternative evaluation measures to correctness. We discovered that the rules extracted through our strategy can cover more resources than the frequency-based strategy and perform this without rule explosion; moreover, our synthetics are useful for increasing the certainty level of correctness results. Finally, our alternative measures offer a wider evaluation profile for policy mining.
