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// Other services

Port 353: NDSAUTH

Port 353 is assigned by IANA to ndsauth (NDSAUTH).

353

How ndsauth works

Other services
client:353ndsauthresponse client:353ndsauthresponse

The client sends a request to port 353 and the ndsauth service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Other services
01 Security

Is port 353 dangerous?

We have no specific security note for port 353. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 353

ServicePortTransportDescriptionReferenceUpdated
ndsauth 353 TCP, UDP NDSAUTH - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 353, and is it reachable?

Linux

sudo ss -ltnup 'sport = :353'      # process listening on 353
sudo lsof -nP -i :353

macOS

sudo lsof -nP -i :353

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 353 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 353
netstat -ano | findstr :353

From another machine

nmap -p 353 -sV <host>
sudo nmap -sU -p 353 <host>
nc -zv <host> 353

Block it in the firewall

sudo ufw deny 353/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 353" -Direction Inbound -LocalPort 353 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 353 used for?

Port 353 is assigned by IANA to ndsauth (NDSAUTH).

Is port 353 TCP or UDP?

Port 353 is registered for TCP and UDP.

Is it safe to open port 353?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 353 is open?

On Linux run "ss -ltnup 'sport = :353'", on macOS "lsof -nP -i :353", and on Windows "netstat -ano | findstr :353" to see the local process. From another machine, "nmap -p 353 <host>" shows whether it is reachable.

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