penetration
1. The intentional passage, through a building wall or partition, or an equipment enclosure or chassis, of a signal-bearing communications medium, e.g., a cable, metallic or optical.
2. Unintended access to the information within a communications or information-processing device via a metallic path intended for another purpose, e.g., via the primary power connection .
3. [The] unauthorized act of bypassing the security mechanisms of a system. [INFOSEC-99]
4. The passage of an rf signal through a physical barrier, such as a partition, a wall, a building, or earth.
5. Unauthorized access to a data processing system. [2382-pt.8]