Common Ports & Protocols Reference ⚡

⚡ Quick Reference — Security-critical ports and protocols

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Must-Know Ports

Port	Protocol	Service	Security Notes
20	TCP	FTP Data	Cleartext — use SFTP
21	TCP	FTP Control	Cleartext credentials ❌
22	TCP	SSH	Secure remote access ✅
23	TCP	Telnet	Cleartext — NEVER use ❌
25	TCP	SMTP	Email sending — target for spam
53	TCP/UDP	DNS	DNS attacks, tunnelling
67/68	UDP	DHCP	Rogue DHCP server attacks
69	UDP	TFTP	No authentication ❌
80	TCP	HTTP	Unencrypted web ❌
110	TCP	POP3	Email retrieval — cleartext
111	TCP/UDP	RPCbind	Common target on Linux
135	TCP	MS RPC	Windows — often exploited
137-139	TCP/UDP	NetBIOS	Windows shares — enumeration target
143	TCP	IMAP	Email — cleartext
161/162	UDP	SNMP	Default community string “public” ❌
389	TCP	LDAP	Directory services
443	TCP	HTTPS	Encrypted web ✅
445	TCP	SMB	Windows file sharing — WannaCry target
993	TCP	IMAPS	Encrypted IMAP ✅
995	TCP	POP3S	Encrypted POP3 ✅
1433	TCP	MS SQL	Database — often exposed
1521	TCP	Oracle DB	Database
3306	TCP	MySQL	Database — often exposed
3389	TCP	RDP	Remote Desktop — brute force target
5432	TCP	PostgreSQL	Database
5900	TCP	VNC	Remote display — often weak auth
6379	TCP	Redis	Often no authentication
8080	TCP	HTTP Alt	Alternative HTTP / proxy
8443	TCP	HTTPS Alt	Alternative HTTPS
27017	TCP	MongoDB	Often no authentication

Secure vs Insecure Protocols

Insecure	Port	Secure Alternative	Port
HTTP	80	HTTPS	443
FTP	21	SFTP/SCP	22
Telnet	23	SSH	22
POP3	110	POP3S	995
IMAP	143	IMAPS	993
SMTP	25	SMTPS	465/587
SNMP v1/v2	161	SNMP v3	161
LDAP	389	LDAPS	636