Sedative: Pacify the Online Social Networks Under Hijacking-Based Troll Attacks

In online communities, trolling disrupts constructive discussion, fuels conflicts, and even triggers offline violence. While many defense techniques assume trolling arises from endogenous user behavior, our research unveils a different dimension: attackers control a group of accounts through hacking or payoffs, and intentionally sow discord by posting specifically designed statements. This attack is considered as a hijacking-based troll attack. Based on the Fridkin-Johnson opinion dynamics model, we formalize how such attacks propagate and accordingly propose Sedative, a real-time defense framework grounded in the concept of attraction basins in complex systems. Sedative identifies and protects structurally and dynamically critical nodes that constitute the backbone of the stable attraction basin to constrain perturbation spread under limited defense budgets. By focusing on localized, real-time influence rather than global computation, Sedative achieves high scalability and responsiveness. Experiments on real and synthetic networks show that Sedative suppresses up to 98 % of attack-induced conflict, significantly outperforming the baselines.