I have a “landline” VoIP number, used by my parents to reach me when my phone is turned off. Apparently, landlines number are preferred by spammers, so I wrote a simple firewall zero-trust configuration for my FRITZ!Box.

The firewall is permitting all numbers included in the address book.

Let’s see how to configure it:

1. Add all trusted numbers to the phone book (Telephony > Telephone Book).
2. Optionally configure an answering machine (Telephony > Answering Machine).
3. Configure the firewall (Telephony > Call Handling > Call Diversion) as follows:

In my case:

• all trusted incoming calls are routed to a telephone connected to port FON1;
• the answering machine on FRITZ!Box is disabled;
• I’m using the answering machine provided by the VoIP provider.