21 FTP – Sends credentials in plaintext.
23 TELNET – Unencrypted remote terminal traffic.
25 SMTP – Emails can be intercepted during transit.
37 TIME – Legacy protocol, rarely used today.
53 DNS – Traffic is vulnerable to spoofing.
80 HTTP – Web traffic is not encrypted.
143 IMAP – Email retrieval without encryption.
445 SMB – File sharing transmitted unencrypted.
389 LDAP – Directory info sent in plaintext.
22 SFTP – Encrypts credentials and data.
22 SSH – Secure remote terminal connectivity.
587 SMTP – SMTP with TLS/SSL encryption.
123 NTP – Secure, modern time sync.
853 DoT – DNS over TLS protects DNS queries.
443 HTTPS – Encrypted web connections.
993 IMAPS – Encrypted email retrieval.
2049 NFS – Secure NFS (recommended behind firewall).
636 LDAPS – LDAP encrypted with SSL/TLS.