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There was a joint statement (released October 7, 2016) from the US Department of Homeland Security (DHS) and the Office of the Director of National Intelligence (ODNI) about recent leaked emails.
The U.S. Intelligence Community (USIC) is confident that the Russian Government directed the recent compromises of e-mails from US persons and institutions, including from US political organizations. [...] We believe, based on the scope and sensitivity of these efforts, that only Russia's senior-most officials could have authorized these activities.
Is there confirmation of the highest levels of Russian government's role behind this, beyond taking the DHS and ODNI's word for it?