Hybrid warfare represents a contemporary form of conflict that integrates conventional military operations with unconventional means, including disinformation campaigns as a key component of information warfare. In this paper, we present an original mathematical model SIR-HW (Susceptible-Infected-Recovered for Hybrid Warfare) for simulating the spread of disinformation in social networks, adapted to the specificities of hybrid warfare in the Baltic region. The model is based on complex network theory and epidemiological models of information spreading, with the introduction of new parameters that reflect the characteristics of the target population: the degree of media literacy, linguistic segmentation of the network, and the effectiveness of institutional countermeasures. Simulations were conducted on synthetic networks that reflect the demographic structure of Baltic societies, with a special focus on the role of nodes with high betweenness centrality in the amplification of disinformation narratives. Results show that network segregation along linguistic lines significantly increases the penetration of disinformation in vulnerable segments of the population, while timely interventions at nodes with high centrality can reduce overall infection by 34–47%. The original contribution of this research lies in the identification of a critical media literacy threshold value (λc ≈ 0.38) below which disinformation campaigns achieve epidemic spreading characteristics, which provides operational implications for formulating policies of resilience to hybrid threats.