CNAME cloacking is a method to hide third party trackers by routing it through first party domains. It is used by Adobe, Criteo, Eularian, etc. When you visit

CNAME cloacking is a method to hide third party trackers by routing it through first party domains. It is used by Adobe, Criteo, Eularian, etc. When you visit example.com , instead of connecting to adserver.com , it connects to random-number.definitely-not-adserver.example.com to evade DNS adblocking and extension blocking. https://medium.com/nextdns/cname-cloaking-the-dangerous-disguise-of-third-party-trackers-195205dc522a https://medium.com/nextdns/cname-cloaking-the-dangerous-disg... For firefox users, uBlock Origin has enabled CNAME blocking by default.