Ports allow multiple services to operate on a single IP address.
Port ranges
- 0-1023: Well-known ports (HTTP=80, HTTPS=443, SSH=22).
- 1024-49151: Registered ports for applications.
- 49152-65535: Dynamic/private ports for temporary connections.
Common services
- 22: SSH (Secure Shell).
- 25: SMTP (Email sending).
- 53: DNS (Domain resolution).
- 443: HTTPS (Secure web).
- 3389: RDP (Remote Desktop).
Security implications
- Open ports increase attack surface.
- Scan for unnecessary services and close unused ports.
- Firewall rules should restrict access by port and IP.
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