Where did you get the information about the 999-XX-XXXX number? If true, that is a no brainer. You are right, those numbers are, usually, assigned to foreign students.
It was a private investigator hired by Orly Taitz who discovered that information about SSN 999-xx-xxxx.
Unfortunately I can’t remember his name right now; when it comes back to me I’ll let you know.
In the meantime, if you can’t wait, the information is posted in a number of threads here on FR. Search for SSN.