Techniques for conducting membership inference attacks are disclosed. In an example, a plurality of target interactions of a target user with an item providing platform are monitored. A plurality of target recommendations for the target user is received from a recommendation system of the item providing platform. Using an attack classifier and based on (i) the plurality of target interactions and (ii) the plurality of target recommendations, an inference is made as to whether at least a subset of the plurality of target interactions and/or at least a subset of the plurality of target recommendations were used to train the recommendation system. The attack classifier is trained using training data associated with a plurality of autonomous users (such as autonomous sock puppets) interacting with the item providing platform. In an example, the item providing platform is one of a video providing platform, an audio providing platform, or a shopping platform.