.COMSEC doesn’t appear to exist as a top-level domain (TLD), according to the exhaustive list provided by the Internet Assigned Numbers Authority (IANA), which is responsible for the global coordination of the Domain Name System (DNS) at the root level (source: IANA).
In the Internet architecture, a top-level domain (TLD) constitutes one of the domains at the highest level in the hierarchical Domain Name System of the Internet (source: IANA). Examples of generic top-level domains (gTLDs) include .com, .org, .net, .gov, .edu, etc., and examples of country code top-level domains (ccTLDs) include .us (United States), .uk (United Kingdom), .fr (France), etc. (source: ICANN).
The term “COMSEC” is an abbreviation for Communications Security, which is the discipline of preventing unauthorized interceptors from accessing telecommunications in an intelligible form, while still delivering content to the intended recipients (source: National Security Institute). In telecommunications, COMSEC is the measure used to deny unauthorized persons information derived from telecommunications of the United States Government related to national security and to ensure the authenticity of such telecommunications (source: Department of Defense, United States). COMSEC includes crypto-security, transmission security, emission security, traffic-flow security and physical security of COMSEC equipment.
To summarize, COMSEC is a term associated with communications and information security, and it’s used specifically within the United States Department of Defense (DOD) and related entities, while a .COMSEC top-level domain does not exist based on the records of the IANA and ICANN, which are the major authorities handling global DNS coordination and internet security respectively.
Sources used:
1. IANA Root Zone Database: https://www.iana.org/domains/root/db
2. ICANN Top-Level Domains: https://newgtlds.icann.org/en/about/tlds
3. National Security Institute: https://nsi.org/
4. US Department of Defense’s Instruction on Communications Security: https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodm/510044\_vol03.pdf?ver=2019-02-21-110926-207
5. Information Assurance Support Environment, United States Department of Defense: https://public.cyber.mil/ia-policy/pci/pci-library/communications-security-comsec/
