Hmm... it seems like a semi-legitimate (maybe a CYA letter?)
The title was "NOTICE OF DATA BREACH", and states: "There was no delay in providing you this notification as a result of law enforcement investigation" it offers some credit monitoring which I can sign up for free ... (NOT!!) and then some Gov't Links and related advice how to protect myself from identity theft.
It didn't ask me for anything, so I don't know. My next door neighbor got the same letters, so ???