999-99-xxxx numbers are not valid Social Security Numbers - by design and function. So they are like unregistered IP addresses of the internet. This is why universities legally use them for foreign nationals. Since they are not in the range of valid numbers there is no harm in using them where a form or computer application requires the social security field to be filled out.
http://cpsr.org/issues/privacy/SSNStructure/
“Invalid SSNs
Any SSN conforming to one of the following criteria is an invalid number:
1. Any field all zeroes (no field of zeroes is ever assigned).
2. First three digits above 770” <-—————
http://www.sinclair.edu/admissions/intladm/EmploymentTaxesFinancial/F1EmploymentF1J1Taxes/
“International students indicate on the Form I-20 that they already have support money and will not need employment. Do not count on employment to support your studies. Off-campus employment is illegal during your first nine months in student status. However, you may work on campus if jobs are available. You first must obtain a valid social security number. If you were assigned a temporary 999-99-XXXX number for use at Sinclair, you cannot use that number for employment.”
Note: “International students....assigned a 999-99-xxxx number” BY THE INSTITUTION. Common and normal practice at colleges to deal with international students who do not have valid SS#.
http://ee.eng.usf.edu/orientation.html
“USF ID Number (UXX-XX-XXXX or a 999-XX-XXX number) or United States Social Security Number. NOTE: International Students - once you have a SS Number, you MUST change your International student ID number (999-XX-XXXX) to your new SS# with the Registrar’s Office. Once you have a SS number, do NOT use your 999 number!”
http://www.shu.edu/applying/graduate/upload/Graduate-Assistantship-Handbook-Revised-2009-04.pdf
“7. International Students. International students who have 999 identification numbers
in Seton Hall’s student system cannot be paid until they obtain a Social Security Card. Information on how to obtain a Social Security Card is available from Office of International Programs, Fahy Hall, Room 128.”
999 = foreign student in almost all cases at a university. Any university.