Network Port: 53
Network Port Reference Guide
Registered Service Name
DNS (Domain Name System)
Transport Protocol
TCP/UDP
Functional Overview
Port 53 is used by DNS query clients to resolve hostnames to IP addresses. UDP is used for standard queries; TCP is used for large zone transfers.
Security Risks & Vulnerabilities
Subject to DNS amplification DDoS attacks, DNS spoofing, and cache poisoning. DNSSEC is recommended to secure signatures.
How to audit network port status
1. Scan Open Ports: Use our Port Scanner utility to verify if this port is actively listening on your host.
2. Verify Encryption: Audit the service layer to confirm SSL/TLS is protecting transmission payload.
3. Hardening Rules: Apply the firewall instructions below to shut down unauthorized inbound ports.
UFW Firewall Rules
Allow Command
sudo ufw allow 53
Block Command
sudo ufw deny 53
iptables Firewall Rules
Allow Command
sudo iptables -A INPUT -p udp --dport 53 -j ACCEPT
Block Command
sudo iptables -A INPUT -p udp --dport 53 -j DROP