Common Firewall Ports Every IT Beginner Should Know
Firewalls filter traffic using ports and protocols. If you’re entering the IT or cybersecurity field, learning commonly used firewall ports is essential. This guide explains important network ports in easy language so you can understand and remember them.
What Are Network Ports?
Ports are virtual communication endpoints used by applications. Just like a house has multiple doors, computers have many network ports. Firewalls decide which ports to allow or block.
Most Common TCP/UDP Ports
| Port | Protocol | Service |
|---|---|---|
| 20/21 | TCP | FTP |
| 22 | TCP | SSH (Remote Login) |
| 23 | TCP | Telnet (Not secure) |
| 25 | TCP | SMTP (Email) |
| 53 | UDP/TCP | DNS |
| 67/68 | UDP | DHCP |
| 80 | TCP | HTTP (Web) |
| 110 | TCP | POP3 (Email) |
| 143 | TCP | IMAP (Email) |
| 443 | TCP | HTTPS (Secure Web) |
| 3389 | TCP | RDP (Windows Remote Desktop) |
| 5060/5061 | UDP/TCP | SIP VoIP |
Why Ports Matter in Firewalls
- Control access to services
- Prevent unauthorized connections
- Secure remote access
- Allow business apps (VoIP, VPN, DNS, etc.)
Blocked vs Allowed Ports
Some ports are commonly blocked to prevent attacks:
- 23 — Telnet (unsecure)
- 445 — SMB (ransomware target)
- 137–139 — NetBIOS
Ports Used in Cyber Attacks
- Port 80/443 — Web attacks (SQL injection, XSS)
- Port 23 — IoT botnet attacks
- Port 445 — WannaCry ransomware
Tips for Beginners
- Never open unnecessary ports
- Use VPN + secure ports like SSH
- Monitor logs for unknown traffic
Understanding ports helps you manage firewalls, secure networks, and troubleshoot connectivity issues. Practice and you will memorize them easily.
