WASHINGTON (AP) — The U.S. is voicing concern over a report that China manipulated Internet traffic intended for a major Chinese Web service company and used it for a cyberattack on U.S. sites.

State Department spokesman Jeff Rathke’s comments Friday follow a recent report by anti-online censorship group Greatfire.org. The group maintains that Chinese authorities carried out denial-of-service attacks, intermittently shutting down San Francisco-based Github.

Github is a U.S.-based web resource that hosts some of the Greatfire.org’s data.

U.S.-government subsidized Greatfire.org produces mirror websites that let Chinese users see information normally blocked by government censors.

Greatfire.org contends that Chinese authorities carried out the attacks by installing malicious code on the computers of users visiting the popular Chinese search engine Baidu and related sites.

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