The paper examines quantitative assessment of wireless distribution system security, as well as an assessment of risks from attacks and security violations. Furthermore, it describes typical security breach and formal attack models and five methods for assessing security. The proposed normalized method for assessing the degree of security assurance operates with at least three characteristics, which allows comparatively analyze heterogeneous information systems. The improved calculating formulas have been proposed for two security assessment methods, and the elements of functional-cost analysis have been applied to calculate the degree of security. To check the results of the analysis, the coefficient of concordance was calculated, which gives opportunity to determine the quality of expert assessment. The simultaneous use of several models to describe attacks and the effectiveness of countering them allows us to create a comprehensive approach to countering modern security threats to information networks at the commercial enterprises and critical infrastructure facilities.