{
  "port": 84,
  "protocol": "tcp",
  "service": "Common Trace Facility (CTF)",
  "oneLiner": "IANA-registered to Common Trace Facility; effectively never seen in the wild.",
  "whatItIs": "Port 84 is registered with IANA as `ctf`, Common Trace Facility, an early tracing/diagnostics service registered by Hugh Thomas. No RFC defines it and no widely deployed implementation uses it, so the registration is the whole of the public record. It still appears in every system `/etc/services` file, which is why scanners label an open 84 as \"ctf\" regardless of what is actually listening. If you find 84 open, treat the name as meaningless and identify the service by its banner.",
  "exposure": {
    "verdict": "careful",
    "note": "Nothing standard runs here, so an open 84 is an unidentified service — fingerprint it before deciding anything."
  },
  "checkCommand": "nc -vz TARGET 84",
  "links": [
    {
      "title": "IANA Service Name and Transport Protocol Port Number Registry",
      "url": "https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml",
      "kind": "iana"
    }
  ]
}