Common Ports Every Cyber Pro Must Know

In cybersecurity & networking, ports are the gateways to communication. If you don’t know them, you’re flying blind. Here are 20 essential ports every IT, networking, or cybersecurity professional must master:

Essential Ports List

🔹 21 – FTP (File Transfer Protocol)

🔹 22 – SSH (Secure Shell)

🔹 23 – Telnet (Unsecured Remote Login)

🔹 25 – SMTP (Email Sending)

🔹 53 – DNS (Domain Name System)

🔹 67/68 – DHCP (Dynamic IP Assignment)

🔹 80 – HTTP (Web Traffic)

🔹 110 – POP3 (Email Retrieval)

🔹 123 – NTP (Network Time Protocol)

🔹 139 – NetBIOS (File Sharing)

🔹 143 – IMAP (Email Access)

🔹 443 – HTTPS (Secure Web Traffic)

🔹 445 – SMB (Windows File Sharing)

🔹 1521 – Oracle DB

🔹 3306 – MySQL DB

🔹 3389 – RDP (Remote Desktop)

🔹 5432 – PostgreSQL DB

🔹 389 – LDAP (Directory Services)

🔹 161 – SNMP (Network Monitoring)

Why This Matters

Cybersecurity Pros: Open ports = attack surfaces. Close unnecessary ones.
Network Engineers: Correct ports ensure seamless communication.
IT Teams: Port checks save hours of debugging.

You Should Know: Practical Commands & Steps

1. Checking Open Ports (Linux/Windows)

Linux (Netstat & Nmap)

netstat -tuln # List listening ports
nmap -sT -O localhost # Scan local machine
sudo ss -tulnp # Modern alternative to netstat

Windows (CMD & PowerShell)

netstat -ano # List active ports
Test-NetConnection -Port 443 -ComputerName google.com # Check remote port

2. Securing Ports (Firewall Management)

Linux (UFW/iptables)

sudo ufw allow 22/tcp # Allow SSH
sudo ufw deny 23 # Block Telnet
sudo iptables -A INPUT -p tcp --dport 80 -j DROP # Block HTTP

Windows (Firewall Rules)

New-NetFirewallRule -DisplayName "Block RDP" -Direction Inbound -LocalPort 3389 -Protocol TCP -Action Block

3. Testing Port Connectivity

Telnet (Deprecated but useful for testing)
```
telnet example.com 80 # Check HTTP port
```

Curl & Netcat (Linux)

curl -I http://example.com # Check web server headers
nc -zv example.com 443 # Test HTTPS port

4. Monitoring & Auditing

Linux (lsof & tcpdump)

sudo lsof -i :22 # See processes using SSH
sudo tcpdump port 53 # Monitor DNS traffic

Windows (Resource Monitor)

Get-NetTCPConnection -State Listen # List listening ports

What Undercode Say

Mastering port management is non-negotiable in cybersecurity. Misconfigured ports lead to breaches, while proper configurations enhance security and efficiency.

🔹 Key Takeaways:

Close unused ports to reduce attack surfaces.
Regularly audit with netstat, nmap, or ufw.
Monitor traffic to detect anomalies early.
Automate security with firewall rules (iptables, Windows Firewall).

Expected Output:

A hardened system with only necessary ports open, monitored, and secured against unauthorized access.

References:

Reported By: Marcelvelica %F0%9D%9F%AE%F0%9D%9F%AC – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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