Salt Typhoon's breach compromises U.S. telecom giants, including T-Mobile, AT&T, and Verizon. The hack exposes vulnerabilities in U.S. wiretapping systems, threatening national security and potentially the data of millions of Americans. T-Mobile claims limited damage, but the full scope of the breach is still unclear.

The Chinese government espionage campaign that has deeply penetrated more than a dozen U.S. telecommunications companies is the “worst telecom hack in our nation’s history — by far,” a senior U.S. senator told The Washington Post in an interview this week.

All the major U.S. carriers, including AT&T, Verizon, and T-Mobile, were impacted, according to the Post. Incredibly, Warner says the hackers are still inside the U.S. system and there’s no obvious way to get them out that doesn’t involve physically replacing old equipment, according to Warner.

A breach of telecoms companies that the United States said was linked to China was the "worst telecom hack in our nation's history - by far," the chairman of the Senate Intelligence Committee told the Washington Post on Thursday.