KRBTGT is the built-in Kerberos service account in Active Directory. Its secret material is used by the Key Distribution Center to sign and validate ticket-granting tickets, which makes it central to domain authentication and trust.
It matters because if an attacker obtains KRBTGT secrets, they may forge Kerberos tickets and impersonate users or services across the domain. In real attacks, the account is often a target of DCSync-style replication abuse, because directory replication rights can expose the data needed to mint valid tickets. Defenders treat KRBTGT as Tier-0: restrict replication permissions, protect domain controllers, monitor for unusual Kerberos ticket activity, and rotate the KRBTGT password carefully when compromise is suspected.