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// Directory & authentication

Port 749: kerberos administration

Port 749 is assigned by IANA to kerberos-adm (kerberos administration).

749

How kerberos-adm works

Directory & authentication
userdirectorykerberos-admresponse userdirectorykerberos-admresponse

The client proves who it is on port 749 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
Well-known (0-1023)
Category
Directory & authentication
01 Security

Is port 749 dangerous?

We have no specific security note for port 749. 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 749

ServicePortTransportDescriptionReferenceUpdated
kerberos-adm 749 TCP, UDP kerberos administration - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 749, and is it reachable?

Linux

sudo ss -ltnup 'sport = :749'      # process listening on 749
sudo lsof -nP -i :749

macOS

sudo lsof -nP -i :749

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 749 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 749
netstat -ano | findstr :749

From another machine

nmap -p 749 -sV <host>
sudo nmap -sU -p 749 <host>
nc -zv <host> 749

Block it in the firewall

sudo ufw deny 749/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 749" -Direction Inbound -LocalPort 749 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 749 used for?

Port 749 is assigned by IANA to kerberos-adm (kerberos administration).

Is port 749 TCP or UDP?

Port 749 is registered for TCP and UDP.

Is it safe to open port 749?

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 749 is open?

On Linux run "ss -ltnup 'sport = :749'", on macOS "lsof -nP -i :749", and on Windows "netstat -ano | findstr :749" to see the local process. From another machine, "nmap -p 749 <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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