Final answer:
Refresher security training at a command is typically required annually to ensure all personnel are updated with latest security procedures and policies, crucial for maintaining operational security.
Step-by-step explanation:
The frequency of refresher security training required at a command is typically determined by the policies of the specific organization and the regulations governing that sector. However, in many cases, especially within the context of the U.S. Department of Defense or other government entities, refresher security training is generally required annually. This is to ensure that all personnel are up-to-date with the latest security procedures, practices, and policies. Such training is crucial for maintaining operational security and preparedness. It is essential for individuals working in areas where security is a significant concern to stay informed about the latest developments and refresh their skills regularly.