| 摘要 |
Access to a resource such as a telecommunications system is monitored and prevented adaptively on a real-time basis by establishing with the customer, a steady state low level of surveillance and arbitrary intermittent interruption during which the telecommunications company demands authentication, by personal identification number (PIN), of a given fraction of access demands (for example, telephone calls), and, in response to signals indicating that arrival of an alert condition, and preferably at least one prior invalid call, raising the level of authentication demands.
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