On Tuesday, Massachusetts Attorney General Maura Healey announced that she will look into the cyberattack on T-Mobile US Inc (TMUS.O), which compromised the personally identifiable information of over 53 million people.

After the third-largest U.S. cellphone carrier reported the hack on Aug. 16, Attorney General Maura Healey announced the investigation. 

The breach exposed names, birthdays, social security numbers, driver's licence information, PIN numbers, and other personal information of an estimated 13.1 million current and 40 million past, and potential T-Mobile users.

It was one of many cyberattacks in recent years that impacted banks, gas pipelines, and hospitals, among other businesses. 

Healey aims to examine whether the Bellevue, Washington-based corporation has sufficient measures in place to secure consumer information and mobile devices. Last month, the Federal Communications Commission in the United States launched an investigation into the matter. 

According to court records, consumers and other private plaintiffs have filed at least 23 lawsuits against T-Mobile as a result of the data leak. 

On August 16, T-Mobile US Inc (TMUS.O) admitted a data breach but said it has yet to determine if any customer information had been compromised, a day after an online forum claimed that the personal data of over 100 million of its users had been compromised. 

In a blog post, the telecom provider stated that it was certain that the entry point used to obtain the data had been shut down. It did not disclose the number of accounts impacted. 

"We are conducting an extensive analysis alongside digital forensic experts to understand the validity of these claims, and we are coordinating with law enforcement," the company stated. 

According to a report in Vice's Motherboard, the forum post does not specify T-Mobile but the attacker informed Vice that they acquired data on over 100 million individuals from T-Mobile servers. 

Following the news, T-stock Mobile's share dropped 2.8 percent in afternoon trade.