UDP ports open|filtered

[Volfi]

Was informed by my ISP today that some of my ports are opened on UDP and could be missused. I run TCP scan on 0-1024 ports, and all were closed / stealth, but UDP scanners like https://www.ipfingerprints.com/portscan.php show in Advanced mode (SYN Stealth, UDP scan) open|filtered status. What can be done with this?

Of course, firewall is ON and no forwarding active.

 

[L&LD]

'Latest RMerlin firmware' (in your signature) means nothing. Be specific.

Have you checked with another website too?

Try Home of Gibson Research Corporation (grc.com) and use the SheildsUp!! links.

What ports are actually opened? That could help pinpoint the cause too.

Turn off all your client devices.

Test again.

Turn on each client device.

Test again.

It would also be helpful to state what and how you've set up your router too. All the mind readers have left the building.

 

[AndreiV]

And did you look to see what Open: Filtered means ?

open|filtered:
A port is marked as "open|filtered" when the port scanner cannot determine whether it is filtered or open.

 

[Volfi]

Yes, I did looked it up.
I do not assume my ports are actually opened, and ISP is wrong.
But would be nice to have this confirmed here



What do you see here?

Open Port Checker & Scanner | Test Port Forwarding | Internet Protocol Tools

Find what's running on an IP Address.

www.ipfingerprints.com

 

[ColinTaylor]

It's practically impossible to do a valid UDP port scan. Unlike TCP, UDP is a connectionless protocol. So unless you know what application is listening on the server side and can craft a valid request the server will not send a reply. So there's no way to tell whether the port is "open" (i.e. listening) or not.

What do you see here?
https://www.ipfingerprints.com/portscan.php

For the reason explained above that test shows me open|filtered for all UDP ports, even the ones I do have servers listening on.