United States laws do not provide to update fake Social Security numbers with actual numbers: Some DREAMers have been interpreting this guidance as if this is a directive from the USCIS to the employers that they should simply let those with fake, made-up, stolen Social Security numbers to simply change it to their valid numbers. Nothing could be further from the truth. That category is only for those extremely rare instances in which the SSA issues new numbers to victims of identity theft or domestic abuse. Typically, what will happen is that once you submit a completed new I9 form, if the employer participates in the E-Verify program, it will be revealed that you lied on your initial I-9, and that is a perjury (when you provided a false SSN and checked either the "A Citizen of the United States" box or any other box and provided forged green card and/or other documentation), punishable with imprisonment and fines. If the employer does not participate in the EVerify program, they may still cross-check your previous I-9 form and will be within their legal rights to question you and ask for further documentation and/or to report you to law enforcement and/or to fire you.
Will some employers turn their eyes the other way and let it all go through? Absolutely. Many employers who have knowingly hired unauthorized workers or simply failed to put the systems in place to verify the documents presented to them may do the same this time as well, but it is worth knowing for the DREAMers that the process of changing their Social Security numbers at their current workplace is not straightforward and has many legal implications, particularly in form of creating a paper trail of lying on I-9 forms and that can impact future immigration benefits.