CyberHunter
Local dataset, no network
// Other services

Port 688: ApplianceWare managment protocol

Port 688 is assigned by IANA to realm-rusd (ApplianceWare managment protocol).

688

How realm-rusd works

Other services
client:688realm-rusdresponse client:688realm-rusdresponse

The client sends a request to port 688 and the realm-rusd service answers.

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
Other services
01 Security

Is port 688 dangerous?

We have no specific security note for port 688. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 688

ServicePortTransportDescriptionReferenceUpdated
realm-rusd 688 TCP, UDP ApplianceWare managment protocol - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 688, and is it reachable?

Linux

sudo ss -ltnup 'sport = :688'      # process listening on 688
sudo lsof -nP -i :688

macOS

sudo lsof -nP -i :688

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 688 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 688
netstat -ano | findstr :688

From another machine

nmap -p 688 -sV <host>
sudo nmap -sU -p 688 <host>
nc -zv <host> 688

Block it in the firewall

sudo ufw deny 688/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 688" -Direction Inbound -LocalPort 688 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 688 used for?

Port 688 is assigned by IANA to realm-rusd (ApplianceWare managment protocol).

Is port 688 TCP or UDP?

Port 688 is registered for TCP and UDP.

Is it safe to open port 688?

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. Close the port if nothing on the host needs it.

How do I check if port 688 is open?

On Linux run "ss -ltnup 'sport = :688'", on macOS "lsof -nP -i :688", and on Windows "netstat -ano | findstr :688" to see the local process. From another machine, "nmap -p 688 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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