I noticed that devices (iPhone) on my Taiwan network were using Russian based trackers and ad utilities, so I created a few aliases to be used in the firewall to block all incoming and outgoing traffic to mail.ru and yandex.ru. These files can also be used as feeds for IP blocking in pfBlockerNG.
https://gist.githubusercontent.com/Ricks-Lab/0cd738226bdea16237e6765430481bf3/raw/mailru.txt https://gist.githubusercontent.com/Ricks-Lab/0cd738226bdea16237e6765430481bf3/raw/mailruv6.txt