China’s cyber campaign known as Salt Typhoon has crossed directly into the US legislative branch, underscoring the exposure of political institutions to long-running intrusions into American communications networks.

Chinese intelligence accessed email systems used by staffers on several powerful US House of Representatives committees, according to people familiar with the incident. These included the House China committee as well as aides working for the foreign affairs, intelligence, and armed services committees. The intrusions were detected in December, though officials said it remains unclear whether lawmakers’ own email accounts were accessed.

“Unless You’re Encrypted”

Salt Typhoon is operated by China’s Ministry of State Security and has been active for several years. According to people familiar with the campaign, it enables access to unencrypted phone calls, text messages, and voicemails across US telecom networks and in some cases allows intrusions into email accounts. Over the past 2 years, the operation has also intercepted calls involving senior US officials.

In December, Mark Warner, the top Democrat on the Senate intelligence committee, warned that the scale of the threat was being underestimated. “Unless you’re on an encrypted device, they can pick any one of us,” Warner told the Defense Writers Group, describing US networks as particularly exposed because many were built when cybersecurity was not a priority.

Telecom Vulnerabilities and Cost Constraints

US telecom providers have struggled to harden their networks against Salt Typhoon, largely because of the high financial cost involved. Jake Sullivan said last year that US telecom companies were “highly vulnerable” to the campaign. The intrusions reflect structural weaknesses rather than isolated security failures.

Salt Typhoon is one of several Chinese cyber espionage efforts targeting US infrastructure. In 2024, the Federal Bureau of Investigation and other agencies said a separate Chinese state-sponsored group, known as Volt Typhoon, had penetrated US energy, transportation, and communications systems in ways that could be leveraged during a conflict.

Sanctions Deferred, Allegations Denied

The US Treasury had planned to impose sanctions on MSS-linked entities over Salt Typhoon in December but reversed course amid concerns the move could undermine a diplomatic détente reached by Presidents Donald Trump and Xi Jinping in October. The four targeted House committees declined to comment on the incident.

China’s embassy in Washington rejected the accusations. Liu Pengyu, a spokesperson, said Beijing “firmly oppose[s] the US side making unfounded speculation and accusations, using cyber security to smear and slander China, and spreading all kinds of disinformation about the so-called Chinese hacking threats.”