Abstract: Disclosed is a behavior detection system for detecting an abnormal behavior, can perform dynamic control based on situation information and a profile of each user to cope with an element threatening security of an internal infrastructure of an enterprise, such as information leakage, in BYOD and smart work environment. The system calculates probabilities of behaviors occurring for respective connection behavior elements, calculates standard deviations of the probabilities based on weighting factors and determines whether or not the calculated behavior occurrence probabilities and behavior standard deviation correspond to a normal behavior, existence of an abnormal connection behavior in a BYOD and smart work environment is detected and an abnormal user is detected by examining whether or not an average traffic volume, an average use time and traffic volume with respect to a use time exceeds respective standard values.