How Dataset Characteristics Affect the Robustness of Collaborative Recommendation Models

Shilling attacks against collaborative filtering (CF) models are characterized by several fake user profiles mounted on the system by an adversarial party to harvest recommendation outcomes toward a malicious desire. The vulnerability of CF models is directly tied with their reliance on the underlying interaction data ---like user-item rating matrix (URM) --- to train their models and their inherent inability to distinguish genuine profiles from non-genuine ones. The majority of works conducted so far for analyzing shilling attacks mainly focused on properties such as confronted recommendation models, recommendation outputs, and even users under attack. The under-researched element has been the impact of data characteristics on the effectiveness of shilling attacks on CF models. Toward this goal, this work presents a systematic and in-depth study by using an analytical modeling approach built on a regression model to test the hypothesis of whether URM properties can impact the outcome of CF recommenders under a shilling attack. We ran extensive experiments involving 97200 simulations on three different domains (movie, business, and music), and showed that URM properties considerably affect the robustness of CF models in shilling attack scenarios. Obtained results can be of great help for the system designer in understanding the cause of variations in a recommender system performance due to a shilling attack.