Which DoD cyberspace domain is classified up to SECRET//NOFORN?

The correct answer is SIPR, which stands for Secret Internet Protocol Router Network. SIPR is a network specifically designed for the handling of classified information at the Secret level and is utilized primarily by the Department of Defense and other designated U.S. government agencies. The designation allows users to access, send, and receive classified information up to the SECRET level, including sensitive operational and strategic communications.

This network supports secure communications, protecting classified data from unauthorized access, which is vital for national security and defense operations. The term SECRET//NOFORN indicates that the information is not only classified but also cannot be shared with foreign nationals, enhancing the security protocols in place.

In contrast, JWICS refers to the Joint Worldwide Intelligence Communications System and operates at a higher classification level, while NIPR (Non-classified Internet Protocol Router) is used for unclassified communications and DISN (Defense Information System Network) encompasses various services and capabilities, not limited to classified information. Therefore, SIPR is distinctly recognized for its capability to handle SECRET-level data.