Sarah Krouse, Dustin Volz, Aruna Viswanatha and Robert McMillan:

A cyberattack tied to the Chinese government penetrated the networks of a swath of U.S. broadband providers, potentially accessing information from systems the federal government uses for court-authorized network wiretapping requests.

For months or longer, the hackers might have held access to network infrastructure used to cooperate with lawful U.S. requests for communications data, according to people familiar with the matter, which amounts to a major national security risk. The attackers also had access to other tranches of more generic internet traffic, they said.