The middle-aged man-call him john-peered at the numbers rolling across his computer monitor, which provided the only illumination in the cramped basement. One number, 307, caught his eye. Like the others, it designated a port, or gateway, between a certain corporation's computers and the outside world. John had just run a program on his PC that sent electronic probes throughout the corporation's network to find a complete list of these ports. Port 307 was "open"-any data coming through it could be displayed on John's screen. Would the information prove useful?

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