The problem is that SSNs are used for both identity and authentication. It’s as if your login was just a username, no password. Equifax et al only need to know

The problem is that SSNs are used for both identity and authentication. It’s as if your login was just a username, no password. Equifax et al only need to know your “username” and still allow for credit checks. But since all we have is SSN, Equifax has your “password” as well, turning a data breach from a theft of private data into a wide open avenue for identity theft.