The methodical going is examined near determination of critical size of index of threat of origin an extraordinary situation in the conditions of the use in the mathematical model of information which has stochastic nature. The index of threat is presented scalar. It is suggested to carry out determination of critical size of index of threat on the basis of providing of necessary probability of authentication of fact of origin of extraordinary situation. Providing of necessary probability is carried out by determination of necessary probability for every type of information proportional influence on the index of threat.
authentication of fact of origin, chance of information, critical size of index of threat