Recommender systems are often susceptible to well-crafted fake profiles,
leading to biased recommendations. Among existing defense methods,
data-processing-based methods inevitably exclude normal samples, while
model-based methods struggle to enjoy both generalization and robustness. To
this end, we suggest integrating data processing and the robust model to
propose a general framework, Triple Cooperative Defense (TCD), which employs
three cooperative models that mutually enhance data and thereby improve
recommendation robustness. Furthermore, Considering that existing attacks
struggle to balance bi-level optimization and efficiency, we revisit poisoning
attacks in recommender systems and introduce an efficient attack strategy,
Co-training Attack (Co-Attack), which cooperatively optimizes the attack
optimization and model training, considering the bi-level setting while
maintaining attack efficiency. Moreover, we reveal a potential reason for the
insufficient threat of existing attacks is their default assumption of
optimizing attacks in undefended scenarios. This overly optimistic setting
limits the potential of attacks. Consequently, we put forth a Game-based
Co-training Attack (GCoAttack), which frames the proposed CoAttack and TCD as a
game-theoretic process, thoroughly exploring CoAttack's attack potential in the
cooperative training of attack and defense. Extensive experiments on three real
datasets demonstrate TCD's superiority in enhancing model robustness.
Additionally, we verify that the two proposed attack strategies significantly
outperform existing attacks, with game-based GCoAttack posing a greater
poisoning threat than CoAttack.

推荐系统中的假账号是一个严重的问题，本论文提出了一个三重协同防御的框架（TCD），旨在通过集成数据处理和鲁棒模型来提高推荐系统的鲁棒性。此外，论文还介绍了一种高效的攻击策略（Co-Training Attack），并将其与 TCD 作为一个博弈过程进行建模，从而全面研究了攻击和防御的潜力。实验证明，TCD 在提高模型鲁棒性方面表现卓越，同时提出的两种攻击策略相比现有攻击也更具威胁性。