How secure is your social security number (SSN) if someone can readily crack it?
According to this article, Boffins guess social security numbers via public data, it is possible to guess the first five digits of a SSN. That leaves four more digits to crack by brute force (trying each one until you hit the correct one).
Armed with publicly available information about where and when an individual was born, researchers from Carnegie Mellon University were able to guess the first five digits of a SSN on the first try for 44 percent of people born after 1989. The success rate balloons to as high as 90 percent for individuals born after 1989 in less populous states such as Vermont. Success rates also rise when the researchers got more guesses. The first five digits for six of 10 SSNs can be identified with just two attempts.
If that doesn't make you nervous, think about this: the last four digits are the ones most often used to verify an SSN. So they're much more readily available than the whole thing. Which means a freelance socialist may not have to brute force it.