Phreaking
Example: "His phreaking skills allowed him to bypass the central telephone switches."
Phreaking refers to experimenting with or exploiting a telephone system and is often considered to be the predecessor of computer hacking. Early phreaking techniques allowed users to bypass telephone company switches and make free long distance calls. This activity later evolved into using modems to gain unauthorized access to computer systems. Phreaking is much less common today than in past decades since cell phone companies offer free long distance service and digital telephone systems are more secure.