Which of the following is NOT one of the four areas of COMSEC?

The correct answer is C, Personnel Security. In the context of COMSEC, which stands for Communications Security, the four main areas typically include Crypto Security, Transmission Security, and Emission Security.

Crypto Security involves protecting cryptographic keys and methods used to encrypt sensitive communications to prevent unauthorized access. Transmission Security focuses on safeguarding the transmissions themselves, ensuring that data sent over communication channels is secure against interception. Emission Security aims to protect against vulnerabilities that arise from unintentional signals emitted by communication systems that could be intercepted by adversaries.

Personnel Security, while important in the broader context of information security, primarily focuses on ensuring that individuals who have access to classified or sensitive information are properly vetted and authorized. It does not specifically pertain to the technical aspects of securing communications, which is why it is not considered one of the four areas of COMSEC.