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// Directory & authentication

Port 4604: Identity Registration Protocol

Port 4604 is assigned by IANA to irp (Identity Registration Protocol).

4604

How irp works

Directory & authentication
userdirectoryirpresponse userdirectoryirpresponse

The client proves who it is on port 4604 and gets an answer (or a ticket) it can use with other services.

Transport
TCP
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 4604 dangerous?

We have no specific security note for port 4604. 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 4604

ServicePortTransportDescriptionReferenceUpdated
irp 4604 TCP Identity Registration Protocol - 2014-08-26
-4604-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 4604, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4604'      # process listening on 4604
sudo lsof -nP -i :4604

macOS

sudo lsof -nP -i :4604

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4604 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4604
netstat -ano | findstr :4604

From another machine

nmap -p 4604 -sV <host>
nc -zv <host> 4604

Block it in the firewall

sudo ufw deny 4604/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4604" -Direction Inbound -LocalPort 4604 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4604 used for?

Port 4604 is assigned by IANA to irp (Identity Registration Protocol).

Is port 4604 TCP or UDP?

Port 4604 is registered for TCP.

Is it safe to open port 4604?

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 4604 is open?

On Linux run "ss -ltnup 'sport = :4604'", on macOS "lsof -nP -i :4604", and on Windows "netstat -ano | findstr :4604" to see the local process. From another machine, "nmap -p 4604 <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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