The Implications of Predictable SSNs

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Two researchers from Carnegie Mellon University recently released a study showing that social security numbers (SSNs) can be predicted with a fairly high degree of accuracy by knowing just a few bits of personal information.  For example, with knowledge of a person’s birth date and town of birth, they were able to predict the SSN of 8.5% of people born between 1989 an 2003 with fewer than 1000 attempts.  The reason that this works is that SSNs are not randomly assigned, but instead are based on a complex yet regular (and thus predictable) pattern.

This research is of more than just an academic interest.  It has real implications for identity fraud and how to protect yourself from becoming a victim.  So how could a malicious person or organization could use this research to commit identity theft?  Since all one needs to know to be able to predict someone’s SSN is date of birth and hometown, the best place to begin is on a social networking site such as Facebook or Myspace.  Many people freely provide this information not only to their “friends”, but often to everyone.  It is easy to find out when and where just about anyone was born on these types of sites.  And even if you are careful about sharing this information only with friends, many people accept friendship invitations from just about anyone.  If I were targeting someone in particular who’s identity I wanted to steal, I would simply try to befriend some of their contacts before sending them a friend request.  This would lend credibility to the friendship request and make them more likely to accept it.  With a little social engineering, it would not be very difficult to determine the necessary personal information for just about anyone.

The next step would be to use the methods described in the research to predict a set of SSNs for the targeted victims.  Once a list of probable SSNs has been generated, it is possible to use online resources, such as instant online credit approval services or the Social Security Administration verification database, to verify correct SSNs.   Once someone has the name, birth date, hometown and SSN of someone, it is then very easy to steal their identity or obtain credit in their name.  All of this could easily be automated to increase the speed and efficiency of obtaining SSNs, making this a legitimate threat to the safety of personal information.  To protect yourself, be very careful about how much information you share on social networking sites and only accept known people into your online networks.

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