Which phrase indicates that achieving a completely secure network is infeasible?

• A. Breadth of the perimeter
• B. Defense in depth
• C. Security by obscurity
• D. Death of the perimeter

Answer: (D)

The idea being tested is that a completely secure network isn’t realistically achievable because modern environments blur the traditional network edge and threats come from multiple directions. The phrase that signals this reality is “Death of the perimeter”—it says the old idea of a hard, well-defined boundary protecting everything inside is no longer feasible, so security must be pervasive, continuous, and based on trust no matter where you are or what device is used. In practice this leads to approaches like zero trust, strict identity and access controls, network segmentation, and constant monitoring, rather than relying on a single boundary to keep attackers out. The other phrases don’t express this feasibility issue: expanding the boundary suggests simply enlarging the edge, defense in depth is about layering protections but still assumes a boundary exists, and security by obscurity relies on hiding details rather than addressing how networks are actually attacked.