What type of emanations are countermeasures intended to contain?

Countermeasures are specifically designed to contain compromising emanations, which are unintended signals that may leak sensitive information from electronic devices. These emanations can include electromagnetic signals produced by computers or other devices, which, if intercepted, could reveal confidential data or communications. By implementing countermeasures, organizations aim to protect against risks associated with these vulnerabilities, ensuring that classified and sensitive information remains secure from unintended disclosure or espionage.

The other options refer to types of emanations that do not typically involve the security concerns associated with information leakage. For example, visible light emanations are commonly part of normal visibility and do not pose a risk of compromising sensitive data. Acoustic emanations may involve sound but aren't generally classified as compromising in the same context as electromagnetic signals. Non-visible light emanations like infrared may have niche implications, but they do not directly relate to the security focus on compromising emanations. Thus, the focus on compromising emanations underlines the importance of safeguarding against data leaks that could endanger national security or sensitive organizational information.