The San Francisco Chronicle reports that hackers breached the networks of Medtronic, Boston Scientific and St. Jude Medical sometime during the first half of 2013 (h/t Help Net Security).

According to the report, the breaches may have lasted as long as several months.

An anonymous source told the Chronicle that the attacks were "very thorough" and appeared to have been committed by hackers in China, though it's not yet clear what data the hackers were targeting. According to the source, the companies weren't aware of the breaches until they were informed of them by federal authorities.

Boston Scientific senior vice president of corporate affairs and communications would only say that the Chronicle's information is "inaccurate," and said, "Like many companies, Boston Scientific experiences attempts to penetrate our networks and systems and we take such attempts seriously. We have a dedicated team of detect and mitigate attacks when they occur as well as to implement solutions to prevent future attacks."

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