[From RISKS Forum Digest 17.28.] Date: Sun, 20 Aug 1995 09:35:01 -0500 From: Quentin Fennessy Subject: Medicare leak through FOIA analysis and 9-digit ZIP I read an article on Medicare in the 20 Aug 1995 _Austin American-Statesman_. The article was evidently done for the Cox Newspaper chain. The article talks of the deterioration of the service, and also touches on that fact that a handful of doctors earn a disproportionate share of Medicare funds paid out. The article has a sidebar, which says, in short: Cox analyzed 100 million computerized Medicare payment records for the report. The information was obtained via FOIA. The doctors names were not released. Evidently there is an ongoing court case to release the doctors' names. Cox was able to identify some of the doctors. The doctor's id codes were obscured by Medicare, but the 9 digit zip codes of the doctor's offices were not. Cox was able to pinpoint individual doctors given this level of detail. Risks: If information needs to be split into private and public components then care needs to be taken for the job to be done correctly. 9-digit zip codes divide the US into fairly small areas and so can (and have) given away the store. This is not to say that I think this Medicare information should be kept secret. However, 9 digit zip codes in databases can be used to pinpoint all sorts of details about folks. Quentin Fennessy quentin.fennessy@sematech.org