Analysis
NAICS 92811 is the 2022 NAICS industry for national security, part of 9281 (National Security and International Affairs).
It has only one more detailed code, 928110, which covers exactly the same activities; the definition, index entries and statistics are on that page.
County Business Patterns excludes public administration, so there is no establishment count for it.
Official definition
See industry description for 928110.
Source: US Census Bureau, NAICS 2022 Manual.