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// Directory & authentication

Port 4129: NuFW authentication protocol

Port 4129 is assigned by IANA to nuauth (NuFW authentication protocol).

4129

How nuauth works

Directory & authentication
userdirectorynuauthresponse userdirectorynuauthresponse

The client proves who it is on port 4129 and gets an answer (or a ticket) it can use with other services.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Directory & authentication
01 Security

Is port 4129 dangerous?

We have no specific security note for port 4129. Its risk depends on the program actually listening on it. General advice for directory & authentication services:

  • Keep directory and authentication services on internal networks.
  • Require signing or TLS and disable anonymous queries.
  • Monitor authentication failures for spraying and brute force.
02 Registry

IANA registry entries for port 4129

ServicePortTransportDescriptionReferenceUpdated
nuauth 4129 TCP, UDP NuFW authentication protocol - 2007-06

// source: IANA service name and port number registry

03 Check it

Which program uses port 4129, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4129'      # process listening on 4129
sudo lsof -nP -i :4129

macOS

sudo lsof -nP -i :4129

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4129 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4129
netstat -ano | findstr :4129

From another machine

nmap -p 4129 -sV <host>
sudo nmap -sU -p 4129 <host>
nc -zv <host> 4129

Block it in the firewall

sudo ufw deny 4129/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4129" -Direction Inbound -LocalPort 4129 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4129 used for?

Port 4129 is assigned by IANA to nuauth (NuFW authentication protocol).

Is port 4129 TCP or UDP?

Port 4129 is registered for TCP and UDP.

Is it safe to open port 4129?

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. Keep directory and authentication services on internal networks.

How do I check if port 4129 is open?

On Linux run "ss -ltnup 'sport = :4129'", on macOS "lsof -nP -i :4129", and on Windows "netstat -ano | findstr :4129" to see the local process. From another machine, "nmap -p 4129 <host>" shows whether it is reachable.

05 Related
:389 LDAP tcp · udp · high risk :636 LDAPS tcp · udp · moderate risk :88 Kerberos tcp · udp · high risk :3268 Global Catalog (LDAP) tcp · udp · high risk :1812 RADIUS udp · tcp · moderate risk :31 MSG Authentication tcp · udp :49 Login Host Protocol (TACACS) tcp · udp :56 XNS Authentication tcp · udp

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