{
  "port": 6666,
  "protocol": "tcp",
  "service": "IRC (alternate)",
  "oneLiner": "One of the five IRC ports in IANA's 6665-6669 ircu range — an alternate to 6667.",
  "whatItIs": "IANA assigns 6665-6669/tcp as a single block named ircu, after the Undernet IRC daemon, and RFC 7194 confirms plaintext IRC is covered by that assignment. Most networks listen on all five so clients have a fallback when one is blocked, and 6666 is the most commonly offered alternate. Its memorable digits also made it a long-standing favourite for command-and-control channels of IRC-controlled bots, which is why some corporate filters block the whole range outright.",
  "exposure": {
    "verdict": "careful",
    "note": "Plaintext IRC — nick, credentials sent to services, and every message travel unencrypted. Prefer 6697 with TLS (RFC 7194) for anything you care about."
  },
  "checkCommand": "printf 'QUIT\\r\\n' | nc -v TARGET 6666",
  "links": [
    {
      "title": "RFC 7194 — Default Port for Internet Relay Chat (IRC) via TLS/SSL",
      "url": "https://www.rfc-editor.org/rfc/rfc7194.html",
      "kind": "spec"
    },
    {
      "title": "IANA Service Name and Transport Protocol Port Number Registry — 6665-6669 (ircu)",
      "url": "https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=6666",
      "kind": "iana"
    },
    {
      "title": "ircu2 — Undernet IRC Daemon",
      "url": "https://github.com/UndernetIRC/ircu2",
      "kind": "github"
    }
  ]
}