Thought Leadership
The unconfirmed data set, which allegedly consists of data from T-Mobile, the second-largest cell phone provider in the US, contains device IDs and phone numbers.
Attackers published the mobile provider’s data in a popular data leak forum and claimed that all 64 million rows of data were up-to-date and dated June 1, 2025.
As Cybernews reports, the leaked sample contains a large amount of sensitive data, including:
- Full names
- Dates of birth
- Tax identification numbers
- Postal addresses
- Telephone numbers
- E-mail addresses
- Device IDs
- Cookie IDs
- IP addresses
Attackers could use the stolen data for identity theft, financial fraud and phishing attacks. For example, malicious actors could use personal data to open fraudulent accounts, file fake tax returns or apply for loans.
Doubts about authenticity – but clear risks
It has not yet been possible to clearly verify whether 64 million individual people are actually affected. Some of the email addresses in the leak already appeared in previous T-Mobile data breaches. Nevertheless, the new data apparently contains information that was not available in earlier leaks, including telephone numbers.
If the leak is authentic, the data protection consequences would be serious. T-Mobile has not yet commented on the incident.
Data leaks in the past at T-Mobile
The T-Mobile group, which belongs to Deutsche Telekom, was the victim of numerous hacker attacks in the 2020s. In October last year, the company agreed to pay a fine of over 15 million US dollars for a series of data breaches.
The settlement involved four separate incidents, two of which affected tens of millions of the mobile providers’ customers. The August 2021 attack affected 76.6 million T-Mobile customers, while the January 2023 attack exposed the data of 37 million people.
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 information to view certain customer data.
With around 131 million customers, T-Mobile is an important market player in the USA. The company generated revenue of over 81 billion US dollars in 2024. Deutsche Telekom is the majority shareholder of the company.
