What does "properly marked classified information" refer to?

The term "properly marked classified information" refers specifically to classified data that displays the appropriate classification level and handling instructions. This means that the information not only indicates its sensitivity but also provides clear guidance on how it should be managed, shared, and accessed, ensuring compliance with security protocols. Proper marking is essential for ensuring that all personnel understand the level of protection required and the procedures to follow when handling the information.

Proper markings typically include clear labels such as "Confidential," "Secret," or "Top Secret," alongside other necessary caveats or restrictions regarding dissemination and handling, enabling the protection of sensitive data throughout its lifecycle. This comprehensive approach ensures that personnel are fully informed about the security requirements associated with the information they are handling.