The paper is devoted to the problem of protecting VoIP systems from DoS/DDoS attacks, as one of the most relevant for the field of digital telecommunications. A review of a significant number of publications by foreign scientists devoted to methods of creating this type of attack, as well as countering them, was carried out. A systematization of the review results is proposed in the form of a comparative table according to the following 10 criteria: year of publication, stage of the life cycle of the attack, its type, protection method, degree of implementation, its resource intensity, practical applicability, effectiveness of the method, application of machine learning. Fundamental conclusions were drawn for each of the criteria, a brief description of the research was given, as well as ways to continue it.