A bit tangential but is there a service or self hosted solution that would take a list of IPs and then keep scanning them periodically and alert me if any new ports have suddenly open?
I just scanned my domain for all 65k ports and it took 20 seconds with a 10gbit pipe. i could scan yours for you and shoot you an email if a new port is discovered. Would charge you Like $100/year or something.
https://www.shodan.io/