The Social Security Admin. (SSA) has issued more than 430 million Social Security numbers (SSN) & cards since the program began in 1935, of which an estimated 300 million belong to living number holders. SSNs have a key role in verifying individuals' authorization to work in the U.S., but SSN cards are also vulnerable to theft & counterfeiting. Concerns about unauthorized workers & the use of counterfeit documents led to this report which: (1) reviews SSA's progress to safeguard the SSN & enhance the card as required under the Intelligence Act; (2) identify key issues to be considered before enhancing the card; & (3) outline the range of options available to SSA for enhancing the card. Includes recommendations. Charts & tables.