This is a bit of a heart-warming story. 10 years ago we were contacted by the Soc. Sec. Admin. Apparently, some illegal was using my son’s #. He had filed a tax return. We assured them our 10 year old son was not working, etc. To make a long story short, we enjoyed that $900 tax return check. They did follow up and assured us they had taken care of the “problem”.
One perp was found working in a state a few hundred miles from my hometown. Don't know the outcome but I'm sure that the "perp" was NOT prosecuted or deported.
In the other case, we (actually they, the SSA) "think" it was used by one person for a short span of time who either left the country or died but they cannot assure me that it is not in the hands of others who aren't working right now or even that only one other person rather than more were using it as the work history was spotty, in different locations and dissimilar jobs.