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// Directory & authentication

Port 3868: DIAMETER

Port 3868 is assigned by IANA to diameter (DIAMETER).

3868

How diameter works

Directory & authentication
userdirectorydiameterresponse userdirectorydiameterresponse

The client proves who it is on port 3868 and gets an answer (or a ticket) it can use with other services.

Transport
TCP · SCTP
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 3868 dangerous?

We have no specific security note for port 3868. 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 3868

ServicePortTransportDescriptionReferenceUpdated
diameter 3868 TCP, SCTP DIAMETER - -
-3868-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 3868, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3868'      # process listening on 3868
sudo lsof -nP -i :3868

macOS

sudo lsof -nP -i :3868

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3868 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3868
netstat -ano | findstr :3868

From another machine

nmap -p 3868 -sV <host>
nc -zv <host> 3868

Block it in the firewall

sudo ufw deny 3868/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3868" -Direction Inbound -LocalPort 3868 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3868 used for?

Port 3868 is assigned by IANA to diameter (DIAMETER).

Is port 3868 TCP or UDP?

Port 3868 is registered for TCP and SCTP.

Is it safe to open port 3868?

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 3868 is open?

On Linux run "ss -ltnup 'sport = :3868'", on macOS "lsof -nP -i :3868", and on Windows "netstat -ano | findstr :3868" to see the local process. From another machine, "nmap -p 3868 <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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