Abstract: A method and apparatus for reducing the vulnerability of the telecommunications system to unauthorized use that is easy to implement and that can reduce the instances of unauthorized access even during periods when telecommunications personnel are not able to give attention to the traffic on the system. The telecommunications system collects statistics of each user's pattern of telecommunications usage. Typically, these statistics will be in the form of, say, the average number of calls per day or the average number of calls per day on given days of the week. It may also include the mean busy hour for the given days of the week. Moreover, daily averages may be taken not only for all calls but also for all calls of a particular type, e.g., of all international calls. These statistics are taken for a reference period, such as the preceding thirty days, and the corresponding quantity for the current day is also computed.