Domain Shadowing: A Stealthy Use of DNS Compromise for Cybercrime https://unit42.paloaltonetworks.com/domain-shadowing/
Domain shadowing https://encyclopedia.kaspersky.com/glossary/domain-shadowing/
Protection from domain shadowing For the owner of the domain the existence of hidden subdomains may be hard to detect because the cybercriminals avoid interfering with the victim’s website or server. Aside from regular checks, the only ways the hacking is likely to become apparent is through user complaints or by the domain being blocked (because of associated malicious activity). Therefore, for domain owners, the main remedy against domain-shadowing attacks is to ensure account security by using strong passwords with two-factor authentication and observing all rules of digital hygiene, thus preventing abuse by outsiders.