{
  "port": 512,
  "protocol": "tcp",
  "service": "exec (BSD rexec)",
  "oneLiner": "BSD rexec — run a command on a remote host, with the username and password sent in cleartext.",
  "whatItIs": "IANA registers TCP 512 as \"exec\": remote process execution with authentication performed using passwords and UNIX login names. A client opens the connection, sends a NUL-separated username, password, and command line, and the rexecd server runs the command and streams back its output. It is the oldest and weakest of the three BSD r-services (512 exec, 513 rlogin, 514 rsh) and virtually every modern distribution ships rexecd disabled or not at all. On UDP the same number is comsat/biff, the local new-mail notifier, which is a different and equally obsolete service.",
  "exposure": {
    "verdict": "never",
    "note": "The password crosses the wire in plaintext on every invocation and the whole session is unencrypted — there is no configuration that makes this safe. Replace it with SSH."
  },
  "checkCommand": "nc -vz -w 3 TARGET 512",
  "links": [
    {
      "title": "IANA Service Name and Transport Protocol Port Number Registry — 512",
      "url": "https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=512",
      "kind": "iana"
    }
  ]
}