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// Other services

Port 5423: VIRTUALUSER

Port 5423 is assigned by IANA to virtualuser (VIRTUALUSER).

5423

How virtualuser works

Other services
client:5423virtualuserresponse client:5423virtualuserresponse

The client sends a request to port 5423 and the virtualuser 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 5423 dangerous?

We have no specific security note for port 5423. 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 5423

ServicePortTransportDescriptionReferenceUpdated
virtualuser 5423 TCP, UDP VIRTUALUSER - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 5423, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5423'      # process listening on 5423
sudo lsof -nP -i :5423

macOS

sudo lsof -nP -i :5423

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5423 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5423
netstat -ano | findstr :5423

From another machine

nmap -p 5423 -sV <host>
sudo nmap -sU -p 5423 <host>
nc -zv <host> 5423

Block it in the firewall

sudo ufw deny 5423/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5423" -Direction Inbound -LocalPort 5423 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5423 used for?

Port 5423 is assigned by IANA to virtualuser (VIRTUALUSER).

Is port 5423 TCP or UDP?

Port 5423 is registered for TCP and UDP.

Is it safe to open port 5423?

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 5423 is open?

On Linux run "ss -ltnup 'sport = :5423'", on macOS "lsof -nP -i :5423", and on Windows "netstat -ano | findstr :5423" to see the local process. From another machine, "nmap -p 5423 <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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