Unitymedia tells open Port 53

Hi There,
my Provider Unitymedia send me a letter.
Open Port 53udp? is open.
I´ve checked this witrh nmap from an external Network.
The result:

53/tcp filtered domain
81/tcp open hosts2-ns
135/tcp filtered msrpc
139/tcp filtered netbios-ssn
179/tcp filtered bgp
222/tcp open rsh-spx
444/tcp open snpp
445/tcp filtered microsoft-ds
3551/tcp open apcupsd

I have no firewall rules in my IP Fire… but why is Port 53 open?

Is there a chance to wright in german? My English is very bad :frowning:


at the old forum i found this: https://forum.ipfire.org/viewtopic.php?f=22&t=23056

here only english is wished.
Translate with https://www.deepl.com if needed.

Tell us please witch router/modem do you have before ipfire

Maybe a check with this https://www.heise.de/security/dienste/Netzwerkcheck-2114.html can help.

You can also find good information here independent of pihole https://discourse.pi-hole.net/t/unitymedia-sicherheitswarnung-open-dns-resolver/2434

You didn’t check Port 53 UDP, but TCP. That’s different so pls check again.

53 is open

Host is up (0.022s latency).
53/udp open|filtered domain

Is it a solution to create a Rule and block 53 udp ?

It definitely is not open by default. You either have a firewall rule or another device in front of your firewall (DSL modem?) is responding.