CyberHunter
LinkedIn profile - Bastien Cordier Email: contact@bastiencordier.pro
// Directory & authentication

Port 3538: IBM Directory Server

Port 3538 is assigned by IANA to ibm-diradm (IBM Directory Server).

3538

How ibm-diradm works

Directory & authentication
userdirectoryibm-diradmresponse userdirectoryibm-diradmresponse

The client proves who it is on port 3538 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 3538 dangerous?

We have no specific security note for port 3538. 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 3538

ServicePortTransportDescriptionReferenceUpdated
ibm-diradm 3538 TCP, UDP IBM Directory Server - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3538, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3538'      # process listening on 3538
sudo lsof -nP -i :3538

macOS

sudo lsof -nP -i :3538

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3538 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3538
netstat -ano | findstr :3538

From another machine

nmap -p 3538 -sV <host>
sudo nmap -sU -p 3538 <host>
nc -zv <host> 3538

Block it in the firewall

sudo ufw deny 3538/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3538" -Direction Inbound -LocalPort 3538 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3538 used for?

Port 3538 is assigned by IANA to ibm-diradm (IBM Directory Server).

Is port 3538 TCP or UDP?

Port 3538 is registered for TCP and UDP.

Is it safe to open port 3538?

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 3538 is open?

On Linux run "ss -ltnup 'sport = :3538'", on macOS "lsof -nP -i :3538", and on Windows "netstat -ano | findstr :3538" to see the local process. From another machine, "nmap -p 3538 <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

Latest vulnerability news

All news