SOS Social Security Number Watch

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Matching a Person to a Social Security Number

Enter the first 3, 5, or 6 digits of a Social Security number (SSN) and select "quick validation" to learn general information about the holder of the SSN. Enter the full 9 digits of a SSN and select "full validation" to additionally learn whether the number is likely to be valid.

- - Example: 078-05-1120 (About this SSN)

Please allow several seconds for a full validation.

   Sample runs

This is an academic demonstration and not fit for any purpose beyond our educational use.


Project Overview

This SSNwatch project has four primary goals related to Social Security numbers (SSNs). These are described below.

  1. Matching people and SSNs
  2. Measuring the identifiability of SSNs, in whole and part
  3. Assessing the public availability of SSNs
  4. Proposing and reviewing technical and policy solutions

  1. Matching People and SSNs

    A goal of the SSNwatch project, presented here, is to explore how publicly available information about people and about Social Security numbers (SSNs) can be used to verify whether a given SSN matches the person presenting the SSN, and vice versa. By identifying the state in which the SSN was issued, the date the SSN was issued, the estimated age range of the recipient, and whether the number has been retired from use, we can provide inferences about the person presenting the SSN. This information can then be matched against other information the person provides for consistency. Mismatches in this information can help identify suspicious presentations of SSNs. Perhaps imposters might be exposed. The SSNwatch Validation Service available above provides such information. In future work, we will also provide inferences in the opposite direction, thereby relating information known about a person to what must be true about their SSN.

    We envision our SSNwatch Validation Service as a way to help combat Identity theft. In the United States, SSNs are essential to recognizing the identity of a person in data. SSNs associate people with various types of health, financial, legal, educational, and billing information. It is not surprising therefore, that SSNs are an essential ingredient to most forms of identity theft. Being able to verify that the person presenting an SSN is the person to whom the SSN was assigned may be useful in recognizing false identities presented by employees, tenants, students, and others.

  2. Measuring the Identifiability of SSNs

    Another goal of this SSNwatch project is to determine the identifiability of an SSN in whole or part. Some people believe that releasing only an SSN, in part or whole, cannot be readily re-identified to the person to whom the SSN was issued without access to credit reports or other information containing both the person's SSN and name explicitly. Such a belief may pose privacy risks for those who's SSNs are released. To demonstrate whether this is merely a myth, we begin by understanding how much and what kind of information is revealed about a person when part or all of the person's SSN is shared. The data within the SSNwatch Validation Service provides the basis for such an assessment.

  3. Assessing the Public Availability of SSNs

    A third goal of this SSNwatch project is to assess the public availability of SSNs, along with related risks. The use of SSNs is clearly widespread. Some people argue that SSNs, while available within many financial, health, employment, and government institutions, is still limited. The claim is that SSNs are not generally available to the public. Recent news reports have surfaced relating the ease at which the SSNs of known people can be purchased for less than $30 each. Our goal in this work is to estimate how active SSNs can be obtained for free and to examine the availability of these SSNs for identity theft and the acquisition of fraudulent credit cards.

  4. Developing and Proposing Technical and Policy Solutions

    Another goal of this SSNwatch project is to provide technical integrations, add-ons and stand-alone technology that render uses of SSNs more socially responsible, and to provide policy and legal analyses that examine the effectiveness of these technologies, and to recommend policy accordingly.

The SSNwatch project is part of our Surveillance of Surveillances (SOS) effort.

Join our mailing list

Join our mailing list to be notified of updates and news about this SSNwatch project. Send an email message to

People on this and Related Projects

This SSNwatch project is provided by

Latanya Sweeney, Ph.D.
Principal Investigator

Data Privacy Lab, a program within IQSS at Harvard University.

Contact us by email at

Students in the Privacy and Anonymity in Data course, who completed course projects related to or using the SSNwatch server:

  • Seth Mandel, SSNs as student identification numbers [article1, article2]
  • Max Tsvetovat, SSNs in Job Bank Resumes
  • Bradford Stanley, SSNs in Job Bank Resumes
  • Yogesh Oka, SSNs and Resumes
  • Saurabh Sharma, SSNs and Resumes
  • Yea-Wen Yang, SSNs and Resumes

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