Which method of transmitting top secret information outside a facility is prohibited by Department of Defense regulations?

The prohibition of using the U.S. Postal Service to transmit top secret information is grounded in security concerns. Department of Defense regulations emphasize the necessity for secure methods of handling sensitive information, especially those classified as top secret. The U.S. Postal Service does not provide the level of security assurance needed for conveying such highly classified materials, making it a vulnerable option for potential interception or unauthorized access.

In contrast, other methods listed, such as using electronic means with a crypto system, the Armed Forces Courier Service, or a designated courier who has been properly cleared, are authorized options. They have established protocols and security measures designed to ensure the integrity and confidentiality of classified information during its transmission. These systems are specifically designed to mitigate risks associated with handling top secret information, unlike standard postal services.