Purple Knight Uncover Active Directory vulnerabilities before attackers do. https://www.purple-knight.com/
KnowBe4 Weak Password Test Weak Password Testing tool will show you how secure your users' network passwords are https://www.knowbe4.com/weak-password-test
Control D Free DNS Resolver https://controld.com/free-dns/
NextDNS The new firewall for the modern Internet https://nextdns.io/
Quad9 A public and free DNS service for a better security https://www.quad9.net
AdGuard DNS ad-blocking DNS server https://adguard-dns.io