CyberHunter
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// Other services

Port 4128: NuFW decision delegation protocol

Port 4128 is assigned by IANA to nufw (NuFW decision delegation protocol).

4128

How nufw works

Other services
client:4128nufwresponse client:4128nufwresponse

The client sends a request to port 4128 and the nufw 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 4128 dangerous?

We have no specific security note for port 4128. 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 4128

ServicePortTransportDescriptionReferenceUpdated
nufw 4128 TCP, UDP NuFW decision delegation protocol - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 4128, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4128'      # process listening on 4128
sudo lsof -nP -i :4128

macOS

sudo lsof -nP -i :4128

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4128 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4128
netstat -ano | findstr :4128

From another machine

nmap -p 4128 -sV <host>
sudo nmap -sU -p 4128 <host>
nc -zv <host> 4128

Block it in the firewall

sudo ufw deny 4128/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4128" -Direction Inbound -LocalPort 4128 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4128 used for?

Port 4128 is assigned by IANA to nufw (NuFW decision delegation protocol).

Is port 4128 TCP or UDP?

Port 4128 is registered for TCP and UDP.

Is it safe to open port 4128?

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 4128 is open?

On Linux run "ss -ltnup 'sport = :4128'", on macOS "lsof -nP -i :4128", and on Windows "netstat -ano | findstr :4128" to see the local process. From another machine, "nmap -p 4128 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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