PGAN: Penalized GANs with Latent Perturbation for Robust Shilling Attack Generation in Recommender Systems

Shilling attacks pose a significant threat to the integrity and reliability of recommender systems by injecting fake user profiles to promote or demote targeted items. Existing generative approaches often suffer from unstable training dynamics and limited realism in the synthesized profiles. In this paper, we propose PGAN, a novel Penalized Generative Adversarial Network enhanced with latent space perturbations to generate high-quality, diverse, and undetectable shilling attack profiles. PGAN incorporates a gradient penalty to stabilize discriminator training and applies controlled noise perturbations in the generator’s latent space to improve robustness and attack diversity. We evaluate PGAN on real-world datasets and show that it consistently outperforms traditional statistical attacks and baseline GAN-based models across multiple evaluation metrics, such as Hit Ratio@K, Prediction Shift, and attack success rate. Experimental results also confirm the realism of the generated profiles through similarity analysis with genuine users. Our proposed model could surpass traditional and state-of-the-art methods, with HR@10 of 0.2051 and 0.2076 on MovieLens and Amazon datasets, respectively.