The scam works like this. They apply for a child tax credit, $1000 per child. Best of all, they don't need an SSN, since they can claim the child is someplace else.
So, you file with an ITN, claim some bogus kids, not only getting any taxes you paid back, but more depending on the kids you claimed.
it costs billions a year.
https://cis.org/Illegal-Immigrants-Receive-Billions-Dollars-More-IRS-They-Pay