Optimal recovery strategies for satellite Internet under advanced persistent threats

With the rapid development of low Earth orbit (LEO) satellite constellations and space information infrastructures, the satellite Internet has become a crucial component of the global information network. However, due to its time-varying links, heterogeneous satellite-ground architecture, and resource-constrained nodes, it exhibits high stealth and defense complexity under advanced persistent threats (APTs). Traditional game-theoretic defense strategies, typically designed for static or semi-static topologies, are inadequate in such highly dynamic environments. To address these challenges, this paper proposes a dynamic and optimal recovery strategy tailored for time-varying satellite networks. First, a dynamic sequential repair game model is established to characterize the adversarial process between the attacker and defender, in which the multi-stage evolution of APT penetration and dynamic defense actions is modeled as a series of sequential zero-sum subgames over a finite time horizon. Then, considering the dynamic evolution of network topology, node heterogeneity, and limited defense resources, an optimal control-based forward-backward search and strategy update algorithm is developed to efficiently compute the game equilibrium with low computational complexity. Simulation results demonstrate that the proposed method effectively mitigates cumulative attack damage and enhances defense robustness under resource constraints.