eli5 Why do scammers always ask for the last 4 digits of your ssn instead of the the whole number, what can they do with the last 4 digits?

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eli5 Why do scammers always ask for the last 4 digits of your ssn instead of the the whole number, what can they do with the last 4 digits?

In: Economics

Your SSN is broken into three parts: area, sequence and serial.

The area (first three numbers) indicate where you were born (or initially issued your SSN). If someone knows this information, they don’t need the first three numbers of your SSN.

The sequence (next two) is based on when you were born. If someone knows when you were born, they don’t need this information.

The serial is unique to you and is almost impossible to guess simply from publicly available information. As such, it’s the most important part of your SSN to safeguard – and the most identifying.

So if I ask you “When and where were you born and what are you last four?”, I now know your entire SSN.

The first digits of a US SSN can be derived. They’re based on where the SSN was issued, as well as when. Only the last 4 digits are allocated without any pattern.

The idea is that you can get more people to take the bait when you only ask for the last 4 digits, so the extra work to derive the first digits is worth it.

A lot of things only ask for your first four. If they can guess a service you already have, they can use that to authorize themselves.

SSN numbers issued after 2011 are random: https://www.ssa.gov/employer/randomization.html

The older ones are formed as described in other comments.