An SPN, or Service Principal Name, is the identifier Kerberos uses to map a network service to the account running it. In Windows and Active Directory environments, SPNs tell the authentication system which service should receive a ticket for a given hostname, port, or service class. Without a correct SPN, clients may not be able to get the right Kerberos ticket.
SPNs matter in cyber security because they sit at the center of service authentication and account trust. Attackers may abuse SPN creation or changes to obtain Kerberos service tickets for Kerberoasting, then try offline password cracking against the associated service account. Defenders should tightly control who can add or modify SPNs, monitor unusual SPN edits, and review whether each service principal is expected. Even a temporary SPN can create a useful ticketing path for abuse.