There’s no such thing as a backdoor that only works when ‘good guys’ use it.
Brief: 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.
Source: Exclusive | U.S. Wiretap Systems Targeted in China-Linked Hack – WSJ (archived due to paywall)