The unconfirmed dataset, supposedly consisting of details taken from America’s second-largest mobile carrier, T-Mobile, includes device IDs and phone numbers. Meanwhile, T-Mobile says that the data in the does not relate to T-Mobile or its customers.
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Hackers claim to have stolen 64 million T-Mobile records containing highly sensitive data.
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The leaked data could enable identity theft, financial fraud, and targeted phishing attacks.
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The breach appears to include some new data points not seen in previous T-Mobile attacks.
Attackers shared the wireless carrier’s details on a popular data leak forum, alleging that all 64 million lines of information are as recent as June 1st, 2025.
T-Mobile responded to Cybernews saying that the data hackers uploaded has nothing to do with the company or its clients.
“Any reports of a T-Mobile data breach are inaccurate. We have reviewed the sample data provided and can confirm the data does not relate to T-Mobile or our customers," the company's representative said.
Meanwhile, the Cybernews research team investigated a data sample attached to the post. Researchers claim that the dataset’s sample was uploaded around 2 a.m. ET and contains a trove of sensitive details, including:
- Full names
- Dates of birth
- Tax IDs
- Full addresses
- Phone numbers
- Email addresses
- Device IDs
- Cookie IDs
- IP addresses
Threat actors could exploit the stolen details for identity theft, financial fraud, and phishing attacks. For example, malicious actors could use personal details to launch fraudulent accounts, file fake tax returns, or attempt to apply for loans.
At the same time, device and cookie IDs, together with IP addresses, can be exploited to collect data about users, learning their online habits. Attackers utilize this type of intelligence for spear phishing attacks on high-value targets.
Data breach verification challenges
However, the team could not accurately determine whether the 64 million lines that attackers claim to have stolen represent an equal number of individuals. Moreover, the Cybernews personal data leak checker indicates that at least some of the emails in the data sample were included in previous T-Mobile breaches.
The team also said that the leak seems to include data points that did not appear in previous leaks, such as phone numbers. However, at this point it is impossible to verify the data with 100% accuracy.
“If this data is legitimate, exposing 64M lines of highly sensitive information poses a serious threat of identity theft/fraud, surveillance, and further, better-targeted attacks on customers,”
the team said.
If the data in the leak were new, researchers believe that individuals impacted face serious privacy concerns.
“It's not the first time T-Mobile has suffered from data breaches, and this raises concerns about persistent security gaps and the effectiveness of protection measures. If this data is legitimate, exposing 64M lines of highly sensitive information poses a serious threat of identity theft/fraud, surveillance, and further, better-targeted attacks on customers,” the team said.
T-Mobile's history of data breaches
The Deutsche Telekom-owned T-Mobile has been the victim of numerous hacker attacks during the 2020s. In October last year, the company agreed to pay a fine of over $15 million for a series of data breaches.
The settlement covered four different incidents, two of which exposed tens of millions of the carriers’ customers. The August 2021 attack exposed 76.6 million T-Mobile customers, while the January 2023 attack revealed details of 37 million individuals.
The settlement also covered the 2022 attack, in which attackers accessed T-Mobile’s management platform, and the 2023 incident, in which attackers stole T-Mobile account credentials to view certain customer details.
T-Mobile is a major market player in the US with around 131 million customers. The company reported revenue exceeding $81 billion in 2024. Deutsche Telekom, a German telecommunications company, is the company's majority shareholder. Deutsche Telekom is the largest in Europe and the fifth largest in the world.
Updated on June 13th [03:25 p.m. GMT] with a statement from T-Mobile.
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