I’ve heard of folks contacting the credit reporting agencies and asking them to flag their SSN. This flagging alerts the agencies when someone is trying to use a certain SSN (in this case, yours). A notice is then sent to the individual saying something along the lines of “someone is trying to attain credit on your SSN”. It also shows up on your credit report so when companies pull it, they know there’s something up with it. I guess this is how people who have been victims of identity theft minimize the chance of it happening again.
Here’s an example thru Equifax: