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 demonstrate that it consistently outperforms traditional statistical attacks and baseline GAN-based models across multiple evaluation metrics, including 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 outperforms traditional and state-of-the-art methods, achieving HR@10 scores of 0.2051 and 0.2076 on the MovieLens and Amazon datasets, respectively.

Recommendation systems have proved to be a compelling performance in overcoming the data overload problem in many domains, such as e-commerce, e-health, and transportation. Recommender systems guide users/clients to personalized recommendations based on their preferences. However, some recommendation systems are vulnerable to shilling attacks, which create rating biases or fake reviews that will eventually affect the authenticity and integrity of the generated recommendations. This survey comprehensively covers various shilling attack methods, including high-knowledge, low-knowledge attacks, and obfuscated attacks. It explores malicious review generators that generate fake text. In addition to that, this survey covers shilling attack detection methods such as supervised, unsupervised, semisupervised, and hybrid techniques. Natural Language Processing techniques are also thoroughly explored for fake text review detection using large language models (LLMs). A wide range of detection mechanisms incorporated in the literature is examined, such as convolutional neural network (CNN), long short term memory (LSTM)-based detectors for rating-based shilling attacks, and bidirectional encoder representation (BERT) and RoBERTa-based detectors for fake reviews that are accompanied by shilling attacks, aiming to offer insights into the evolving methods of shilling attack strategies and the corresponding advancements in the detection methods.

Context-aware recommendation systems (CARSs) leverage contextual information, e.g., time, location, or mood, to generate more personalized recommendations with high accuracy; however, existing CARSs fall short in: 1) handling the high sparsity of data; 2) designing scalable solutions in real time; and 3) providing more personalized solutions with the current limited static contexts. This article proposes a multi-CARS based on consensus clustering (MCARS-CC) to solve these challenges. The item-based contextual information is acquired using explicit static and inferred contexts by applying sentiment analysis to the users’ reviews. The proposed model is experimented using contextual prefiltering and postfiltering techniques applied to two benchmark datasets, Yelp and TripAdvisor. The model is evaluated using mean absolute error (MAE), root-mean-squared error (RMSE), response time, precision, recall, and F-measure. The experimental results show that the proposed MCARS-CC model outperforms other baseline techniques using the accuracy and error-based metrics. Incorporating hypergraph partitioning algorithm (HGPA) could improve the MAE and RMSE by 25.96% and 8.94% (Yelp), respectively. Also, HGPA led to an 18.47% and 15.94% improvement ratio in terms of MAE and RMSE (TripAdvisor), respectively.

In the realm of social network analysis and mining, recommendation systems have become indispensable algorithms in assisting users and industries in navigating the available contents or products in various domains and getting the most personalized recommendations to their interests and preferences. However, if the input data has been generated by malicious users, that poses a significant challenge to recommender systems' reliability and efficiency. One of the main threats that poses a challenge to recommender systems is shilling attacks. Shilling attacks tend to manipulate or poison the data in the systems' training phase, leading to biased or compromised recommendations. To address this challenge, we propose a robust recommender system using variational autoencoders (VAE) with Anomaly detection. Our model learns complex and non-linear patterns by exclusively focusing on the user-item interaction data, represented by a binary user-item interaction matrix, making it more resilient to classic shilling attacks. Moreover, our paper incorporates an anomaly detection mechanism, alongside the autoencoder, that analyzes the reconstruction errors, i.e. (MSE) between the original interactions and their reconstructed ones. We test the model on a real-world dataset and evaluate it using Recall@k and NDCG@k. This work enhances the trustworthiness and accuracy of recommendation algorithms, mainly when deployed in social network analysis and mining, where the potential for malicious data manipulation is a critical concern.