id: expn-mail-detect

info:
  name: EXPN Mail Server Detect
  author: r3dg33k
  severity: info
  description: |
    The "EXPN" can be used by attackers to learn about valid usernames on the target system. On some SMTP servers, EXPN can be used to show the subscribers of a mailing list subscription lists are generally considered to be sensitive information.
  metadata:
    max-request: 1
  tags: mail,expn,network,detect

tcp:
  - inputs:
      - data: "65686c6f20636865636b746c730a"
        type: hex
    read-size: 2048

    host:
      - "{{Hostname}}"
    port: 25

    matchers:
      - type: word
        words:
          - "250-EXPN"
# digest: 490a00463044022047df9aa5f92ea9de229b9a6a1fa56f05af7a5fb984f252ddc352a9c33197a2ac022076c20356e98b1c75ddfb09a2793f492ca75c5ad1918259ea68b0785e91f048b0:922c64590222798bb761d5b6d8e72950