Is this some kind of fishing ground?
This I don't understand. Maybe it's late?
Passwords were hashed using the easy-to-subvert MD5 hash. Reg tech staff, on learning of the breach, say they started using more secure ciphers years before this breach.
Why is Reg tech staff tasked with implementing Yahoo ciphers??
And yes, 10⁹ user accounts sounds more like 10⁹ IoNT (Internet of Needful Things) accounts.