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// Directory & authentication

Port 750: kerberos version iv

Port 750 is assigned by IANA to kerberos-iv (kerberos version iv), loadav (), rfile ().

750

How kerberos-iv works

Directory & authentication
userdirectorykerberos-ivresponse userdirectorykerberos-ivresponse

The client proves who it is on port 750 and gets an answer (or a ticket) it can use with other services.

Transport
UDP · TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned3 registered services
Range
Well-known (0-1023)
Category
Directory & authentication
01 Security

Is port 750 dangerous?

We have no specific security note for port 750. 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 750

ServicePortTransportDescriptionReferenceUpdated
kerberos-iv 750 UDP kerberos version iv - -
loadav 750 UDP - -
rfile 750 TCP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 750, and is it reachable?

Linux

sudo ss -ltnup 'sport = :750'      # process listening on 750
sudo lsof -nP -i :750

macOS

sudo lsof -nP -i :750

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 750 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 750
netstat -ano | findstr :750

From another machine

nmap -p 750 -sV <host>
sudo nmap -sU -p 750 <host>
nc -zv <host> 750

Block it in the firewall

sudo ufw deny 750/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 750" -Direction Inbound -LocalPort 750 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 750 used for?

Port 750 is assigned by IANA to kerberos-iv (kerberos version iv), loadav (), rfile ().

Is port 750 TCP or UDP?

Port 750 is registered for UDP and TCP.

Is it safe to open port 750?

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 750 is open?

On Linux run "ss -ltnup 'sport = :750'", on macOS "lsof -nP -i :750", and on Windows "netstat -ano | findstr :750" to see the local process. From another machine, "nmap -p 750 <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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