Upon scanning LAN network shows ports open: 22, 23, 53 and 80 all are fine OFC. But then 20005 port xcept 4 port btx open (German Telekom’s CEPT videotext service). Searching google and Reddit showed this is some what "security flaw " related to usb storage. I do have a usb modem for internet backup connected.

I tried these Potential Solutions:

1. Update Firmware: no updates.

2. Port Forwarding Configuration: i don't have any.

3. Disabled (UPnP).

4. Disabled parental controls, because removing the list is too much work.

5. Service Filtering: tried to set a rule like:

"Service Type: Any(ALL)   

Protocol: 

TCP

Starting Port:  20005

Ending Port: 20005

Service Type: btx

Filter Service For:All IP Addresses"

-What actually got saved and isn't active (bulb icon active), and cant be deleted or edited (Error code: 9003 Invalid value.):

Trying to delete:

Now scanning shows port closed!

What is going on?