U.S. officials are warning Americans to use encrypted messaging apps like Signal or WhatsApp to safeguard their communications amid a massive cyberespionage campaign linked to the Chinese hacking group “Salt Typhoon,” which is targeting major telecommunications companies, including AT&T, Verizon, and T-Mobile.

The hacking effort is being described as one of the largest intelligence breaches in U.S. history.  First detected in the spring and publicly disclosed in October, the breach has allowed hackers to infiltrate telecommunications networks and access critical information. 

This includes phone call metadata, such as numbers called and call durations, particularly from the Washington, D.C., area. The hackers also intercepted live phone calls of select individuals and accessed telecommunications systems designed for court-ordered surveillance, potentially exposing classified intelligence activities.

The attack affects more than 80 telecommunications and internet service providers globally, including at least eight in the U.S. The intrusion has compromised communications of high-profile targets, including government officials and political figures, raising serious concerns about national security.

Federal agencies, including the FBI, the Cybersecurity and Infrastructure Security Agency (CISA), and the National Security Council, have been working to address the breach. However, during a classified Senate briefing they warned that fully eradicating the hackers may take considerable time, leaving U.S. telecommunications networks vulnerable in the meantime. 

Jeff Greene, CISA’s executive assistant director for cybersecurity, stressed the importance of encryption as a key defensive measure and encouraged Americans to adopt secure communication practices immediately.

The Chinese government has denied involvement, calling the allegations baseless. Executives from affected companies, including Verizon and AT&T, have acknowledged the severity of the intrusion and are collaborating with federal authorities to mitigate its impact.

A Senate Commerce subcommittee will hold a hearing on December 11 to evaluate the risks to communications infrastructure and explore preventive measures.