By CBS 2 Chicago Staff

CHICAGO (CBS) — DuPage Medical Group on Monday said hackers were able to gather personal information of about 600,000 patients.

That information includes names, addresses, dates of birth, diagnosis codes, medical procedure information and treatment dates. In a small number of cases, social security numbers may be been obtained, officials said in a news release.

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The breach happened on July 12-13 and caused a disruption of the medial group’s network. After a month-long forensic investigation, DuPage Medical concluded that certain files that contained patient information were targeted by the hackers.

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“DMG is in the process of mailing letters to a broad and inclusive list of individuals directly whose information may be involved in this incident,” according to the news release.

DuPage Medical Group is offering credit monitoring and identify theft protection at no cost for those affected individuals. Additional information is available by calling 1-800-709-2027 between 8 a.m. and 8 p.m. CST Monday through Friday, or by visiting www.dupagemedicalgroup.com.

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DMG is the largest inde­pen­dent mul­ti-spe­cial­ty physi­cian group in Illinois.

CBS 2 Chicago Staff