Sources.

Number of T-Mobile Customers Confirmed to Be Affected by Hack Reaches 54 Million | SecurityWeek.Com

Eduard Kovacs on August 23, 2021

T-Mobile launched an investigation in response to reports that someone had been offering to sell 100 million T-Mobile customer records on the dark web for roughly $280,000 in bitcoin. The company quickly confirmed the breach, as well as the fact that millions of customers are impacted.  However, the exact number of customers hit by the incident is still being determined, and so is the type of data that was compromised.

T-Mobile initially said the breach impacted approximately 7.8 million current postpaid customer accounts, but it admitted identifying another 5.3 million accounts in its latest update.

In the case of the 7.8 million accounts, compromised data includes name, date of birth, social security number (SSN), driver’s license information, phone number, and IMEI and IMSI information. For the newly identified 5.3 million accounts, the company said the hackers accessed names, addresses, dates of birth, phone numbers, IMEIs, and IMSIs, but not SSNs or driver’s license information.

In its latest update, the carrier said it identified an additional 667,000 compromised accounts belonging to former customers. These accounts stored information such as name, phone number, address, and date of birth, but SSNs or driver’s license information were not included in the records.  The attackers may have also obtained files storing only phone numbers, IMEIs and IMSIs, without personal information.

As for impacted prepaid customers, in addition to the 850,000 current accounts that were initially confirmed to have been compromised, T-Mobile added 52,000 records associated with current Metro by T-Mobile accounts. 

T-Mobile has still not found evidence that the cybercriminals stole credit or debit card information or other financial information.  The company is offering two years of free identity protection services to impacted individuals. T-Mobile has disclosed several data breaches over the past years, including in 2018, 2019, and 2020.

What to do?

Ensure that your software is properly installed and configured.

Ensure your firewall and antivirus/antimalware software is up to date and operational.

Routinely back up your network to a safe location that is “air-gapped.”

What can you do when this happens to you?

If you find that your network has been compromised, immediately shut down

Identify and mitigate the breach and mitigate as soon as possible

Rebuild the network from a known “clean” backup