- 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.
Port 73: Remote Job Service
Port 73 is assigned by IANA to netrjs-3 (Remote Job Service).
73
How netrjs-3 works
Other servicesThe client sends a request to port 73 and the netrjs-3 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
Is port 73 dangerous?
We have no specific security note for port 73. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 73
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| netrjs-3 | 73 | TCP, UDP | Remote Job Service | - | - |
// source: IANA service name and port number registry
Which program uses port 73, and is it reachable?
Linux
sudo ss -ltnup 'sport = :73' # process listening on 73
sudo lsof -nP -i :73macOS
sudo lsof -nP -i :73
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 73 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 73 netstat -ano | findstr :73
From another machine
nmap -p 73 -sV <host> sudo nmap -sU -p 73 <host> nc -zv <host> 73
Block it in the firewall
sudo ufw deny 73/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 73" -Direction Inbound -LocalPort 73 -Protocol TCP -Action Block # Windows
What is port 73 used for?
Port 73 is assigned by IANA to netrjs-3 (Remote Job Service).
Is port 73 TCP or UDP?
Port 73 is registered for TCP and UDP.
Is it safe to open port 73?
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 73 is open?
On Linux run "ss -ltnup 'sport = :73'", on macOS "lsof -nP -i :73", and on Windows "netstat -ano | findstr :73" to see the local process. From another machine, "nmap -p 73 <host>" shows whether it is reachable.
Other other services ports
: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