Northwest Telco Corp. (Telco) provides long-distance telephone service. Customers dial a general access number, then enter a six-digit access code and then the phone number they want to call. A computer places the call and charges the account.

On January 10, 1990, Cal Edwards, a Telco engineer, noticed that Telco’s general access number was being dialed exactly every 40 seconds. After each dialing, a different six-digit number was entered, followed by a particular long-distance number. This continued from 10 PM to 6 AM.

Why was Edwards concerned?