Port

Port 53

Conventionally used by DNS. Port assignments are conventions, so confirm the actual listener before you write a rule around this number.

TCP · UDPEncrypted: No

Protocols on this port

DNS

Name resolution

Security: Tunnelling and C2 channel; validate DNSSEC, log queries, block open recursion

UDP, TCP · Encrypted: No

Where this port appears in the documentation

DNS

The Domain Name System is the distributed, hierarchical directory that resolves names to addresses and service records for nearly every other service.

Exposure guidance

Decide reachability from the identity of the caller, not from the port number. If the service on this port carries credentials or administrative control, restrict it to an administrative network, require strong authentication, and log every session that reaches it.

Nearby ports

Port 25 Port 67

In the knowledge graph

Open the interactive map centred on this entity to see everything it connects to and travel outwards from there.

Explore port 53 in the knowledge graph