DNS

DNS is the internet's address book. You type a name, it returns the number your computer actually connects to.

The consequence people miss is where the real power sits. Whoever controls the address book decides where your traffic goes, regardless of how well your servers are secured. That control lives in the account you hold with whoever you bought the domain from. An attacker who takes that account can point your website and your email wherever they like without touching anything you built. It is frequently the least protected account an organisation owns and the most consequential.