{
  "port": 109,
  "protocol": "tcp",
  "service": "POP2",
  "oneLiner": "Post Office Protocol version 2 — obsolete since POP3 took 110 in 1988.",
  "whatItIs": "POP2, defined in RFC 937, is the second-generation mailbox pickup protocol: a client connects, sends HELO with a username and plaintext password, and retrieves messages with a small command set. POP3 on port 110 replaced it and is not backward compatible, so POP2 has been dead in practice for decades. Some old mail servers still compiled a POP2 listener into inetd, which is the only realistic way you meet it. Like POP3 without TLS, it sends credentials in the clear.",
  "exposure": {
    "verdict": "never",
    "note": "Obsolete protocol with plaintext authentication and no TLS story; if 109 is open, the fix is to turn it off, not to firewall it."
  },
  "checkCommand": "sudo lsof -nP -iTCP:109 -sTCP:LISTEN",
  "links": [
    {
      "title": "RFC 937 — Post Office Protocol Version 2",
      "url": "https://www.rfc-editor.org/rfc/rfc937.html",
      "kind": "spec"
    },
    {
      "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"
    }
  ]
}