What is the security classification denoting the highest level of protection?

The classification level denoting the highest level of protection is Top Secret. This designation is applied to information that, if disclosed, could cause exceptionally grave damage to national security. The criteria for information to be classified as Top Secret include its potential to reveal critical military strategies, intelligence operations, diplomatic negotiations, or other sensitive data that require the utmost safeguard against unauthorized access.

Confidential, Secret, and Restricted classifications represent progressively lower levels of sensitivity and protective measures. Confidential is the lowest of the formal classifications and pertains to information that could cause damage to national security if disclosed. Secret indicates that the information could cause serious damage, whereas Restricted is not one of the formal security classifications in the U.S. system but might refer to certain limited access information or operational details that are not classified but still require protection from unauthorized disclosure. Thus, Top Secret is the correct response as it represents the highest standard of safeguarding sensitive information.