Biden says Russian-linked cyberattack started "last year"

Details: The hack is known to have breached the Departments of Defense, State, Homeland Security, Treasury, Commerce and Energy and its National Nuclear Security Administration — plus the National Institutes of Health.

• Multiple global corporations were also infiltrated.

Our thought bubble: There’s a lot we still don’t know, but the growing list of key federal agencies struck alone is cause for serious concern. This may turn out to be the most consequential hack in U.S. history, and one that has spurred lawmakers of both parties to call for a firm response.

• Trump’s refusal to acknowledge what his own intelligence and national security experts are surely telling him will come as welcome news to the Kremlin.

Go deeper: Trump downplays Russian-linked cyberattack on U.S.