The purpose of the study is to formally formulate the problem of artificial immunization of complex technical systems to ensure their security against cyber threats. The work draws an analogy between human immunity and the security functions of modern technical systems. A mathematical model of a technical system that describes how the system’s immunity counteracts various cyberattacks was developed. The immunization problem is formulated to minimize the number of infected objects in the system and maximize the number of cured objects among the infected ones.