The telecommunications hack earlier this month linked to Chinese hackers was the worst in U.S. history, according to the chairman of the Senate Intelligence Committee.

The FBI and the Cybersecurity and Infrastructure Security Agency (CISA) announced in mid-November that the intelligence community identified that Chinese-linked actors “have compromised networks at multiple telecommunications companies to enable the theft of customer call records data, the compromise of private communications of a limited number of individuals…, and the copying of certain information that was subject to U.S. law enforcement requests.”