FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -DNS uses Port 53 which is nearly always open on systems, firewalls, and clients to transmit DNS queries. Rather than the more familiar Transmission Control Protocol (TCP) these queries use User Datagram Protocol (UDP) because of its low-latency, bandwidth and resource usage compared TCP-equivalent queries.

Detailed explanation-2: -DNS uses the User Datagram Protocol (UDP) on port 53 to serve DNS queries. UDP is preferred because it is fast and has low overhead. A DNS query is a single UDP request from the DNS client followed by a single UDP reply from the server.

Detailed explanation-3: -A DNS server uses well-known port 53 for all its UDP activities and as its server port for TCP. It uses a random port above 1023 for TCP requests. A DNS client uses a random port above 1023 for both UDP and TCP.

Detailed explanation-4: -It means either your computer is running a DNS server (or proxy or it has been compromised and someone is using it as a mechanism to control/access your system). If port 53 is only listening on your LAN it’s likely you have some computer sharing going on and this woukd be normal on a router.

Detailed explanation-5: -Port 53 is the well-known port number for DNS. Many years ago it was common for certain DNS implementations to send queries from source port 53.