membership

Definition

Whether a particular record was part of a model's training set. Membership inference attacks try to decide this from the model's behaviour alone, and their success rate is a standard privacy yardstick: a model that answers noticeably differently on data it has seen is leaking something about individuals in its corpus. It is a weaker target than extraction, which aims to reconstruct the content itself, but membership alone can be sensitive when the dataset is, say, a patient cohort.