T-Mobile has also been targeted by the Chinese threat group Salt Typhoon in a major cyberespionage campaign targeting several telecommunications companies in the United States.

The Wall Street Journal revealed in September that the China-linked threat actor had hacked into the networks of several major US broadband providers, potentially compromising wiretap systems in search of sensitive information. 

The publication later revealed that the list of victims included companies such as Verizon, AT&T and Lumen Technologies, as well as some service providers outside the US. 

Last week, the cybersecurity agency CISA and the FBI confirmed investigating what they described as a broad and significant Chinese cyberespionage campaign targeting telecom infrastructure.

The agencies said hackers had compromised the networks of multiple telecommunications companies to steal customer call record data. 

In addition, their investigation showed “the compromise of private communications of a limited number of individuals who are primarily involved in government or political activity, and the copying of certain information that was subject to U.S. law enforcement requests pursuant to court orders”.

The Wall Street Journal has continued digging into the story and on Friday reported learning from people familiar with the matter that T-Mobile was also targeted by Salt Typhoon as part of this campaign. 

In response to the WSJ report, T-Mobile said it’s “closely monitoring this industry-wide attack”, but noted that it has seen no significant impact to its systems or data, attributing this to its security controls, network structure, and diligent monitoring and response. 

“We have no evidence of access or exfiltration of any customer or other sensitive information as other companies may have experienced,” T-Mobile stated. “We will continue to monitor this closely, working with industry peers and the relevant authorities.”

It’s worth noting that T-Mobile suffered several significant data breaches in recent years, including incidents that impacted tens of millions of customers. 

Bloomberg reported recently that Chinese hackers also breached the systems of Singapore-based telecommunications provider Singtel, likely as part of a test run for attacks targeting US carriers. 

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