In a departure from most medical privacy cases, Anthem Blue Cross said it accidentally posted online Social Security or tax identification numbers for about 24,500 California doctors.
[Updated 1:03 p.m. PST Nov. 25: An Anthem spokesman said Monday that 24,500 doctors were affected, up from the previous 5,900 figure issued by the company.]
Anthem, a unit of insurance giant WellPoint Inc., said the private information was mistakenly included with its online provider directory for about 24 hours late last month.
The state's largest for-profit health insurer said once it identified the error, it removed the information from its website. Anthem said this breach didn't involve any patient data.
Most medical privacy cases involve hospitals or insurers exposing sensitive patient information.
An Anthem spokesman said the company has offered the affected doctors free credit monitoring and credit insurance.
Like many insurers, Anthem has been revamping its provider directory for consumers to reflect changing networks of doctors and hospitals for new policies being offered under the federal healthcare law.
If tax identification or Social Security numbers fall into the wrong hands, they can often be used to file bogus medical claims with insurers and government agencies such as Medicare.
Federal investigators have been trying to clamp down on Medicare billing fraud in recent years, particularly in hot spots such as Southern California.