Registered to the DoD DNSIX security attribute token map; a legacy defense-network registration.
IANA assigns port 90 to dnsix, the DNSIX Security Attribute Token Map, from the US Department of Defense DNSIX (DoD Intelligence Information System Network Security for Information Exchange) work on labeled networking. It is not defined by an RFC and has no general-purpose implementation. Outside classified DoD deployments you will not meet it. An open 90 on an ordinary host is almost always a second web server or admin panel placed near 80.
Expose with care
Whatever is listening is not DNSIX; identify it and apply that service's rules.
$ nc -vz TARGET 90Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.