Involving 37 million users, US telecom operator T-Mobile has been hacked again.

CTOnews.com, January 20 (Xinhua)-- US telecom operator T-Mobile issued a security announcement today, saying that its network was recently hacked and some information involving 37 million users was stolen from it.

T-Mobile said in the announcement that the company closed the access channel within 24 hours after detecting a security attack and prevented hackers from accessing "the most sensitive types of customer data" through system rollback (system fallbacks) measures.

CTOnews.com learned that T-Mobile was subjected to a cyber attack in August 2021, involving 50 million people. In the incident at that time, the user's personal information, including the user's ID number, was stolen. The impact of the attack was relatively mild, officials said in an announcement:

We have contacted the affected users one by one. Through a thorough investigation, we have determined that bad actors use an application programming interface (API) to obtain limited types of information on the account.

Our security team closed the access channel within 24 hours after discovering the problem. Our systems and policies can effectively prevent hackers from accessing the most sensitive types of customer information. Therefore, in this incident, the customer's account and financial information should not have been accessed, and there is no evidence that hackers broke into or damaged T-Mobile 's network or system.

T-Mobile admitted that the hackers stole some of the user's information and wrote in the announcement:

In this incident, the hackers did not have access passwords, payment card information, social security numbers, government ID card numbers or other financial account information. But hackers access some basic customer information (almost all of which are widely found in marketing databases or directories), including name, billing address, email, phone number, date of birth, account number, as well as information such as the number of lines in the account and service planning functions.

T-Mobile 's post on its website did not disclose how many customers were affected by the data breach. However, in filings with the Securities and Exchange Commission, the company said the loophole exposed customer information for 37 million accounts.