- 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 17: Quote of the Day
Port 17 is assigned by IANA to qotd (Quote of the Day).
17
How qotd works
Other servicesThe client sends a request to port 17 and the qotd 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 17 dangerous?
We have no specific security note for port 17. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 17
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| qotd | 17 | TCP, UDP | Quote of the Day | - | - |
// source: IANA service name and port number registry
Which program uses port 17, and is it reachable?
Linux
sudo ss -ltnup 'sport = :17' # process listening on 17
sudo lsof -nP -i :17macOS
sudo lsof -nP -i :17
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 17 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 17 netstat -ano | findstr :17
From another machine
nmap -p 17 -sV <host> sudo nmap -sU -p 17 <host> nc -zv <host> 17
Block it in the firewall
sudo ufw deny 17/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 17" -Direction Inbound -LocalPort 17 -Protocol TCP -Action Block # Windows
What is port 17 used for?
Port 17 is assigned by IANA to qotd (Quote of the Day).
Is port 17 TCP or UDP?
Port 17 is registered for TCP and UDP.
Is it safe to open port 17?
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 17 is open?
On Linux run "ss -ltnup 'sport = :17'", on macOS "lsof -nP -i :17", and on Windows "netstat -ano | findstr :17" to see the local process. From another machine, "nmap -p 17 <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 :18 Message Send Protocol (historic) tcp · udp :27 NSW User System FE tcp · udp