Abstract
The study describes the basic network attacks such as "denial of service", algorithm of operation of malefactors with attacks of this type, techniques of detection of DOS/DDOS/DRDOS attacks in networks of mass service. For detection of DDoS-attacks is offered the valuation method of probability of loss of arbitrary request in case of its passing on networks of mass service. Developed the architecture and constructed program implementation of system of detection of DDoS-attacks. The developed technique allows to receive an adequate assessment of frequency of loss of requests on a network if the network of mass service is in the stationary mode.