New York, October 2

Hackers have stolen personal information belonging to about 15 million T-Mobile wireless customers and potential customers in the US, including social security numbers, home addresses, birth dates and other personal information.

In the latest high-profile breach, the hackers got the information from credit reporting agency Experian, which T-Mobile uses to check the credit of consumers applying for phone plans and financing for devices. Experian said T-Mobile customers who applied between September 1, 2013 and September 16, 2015 may have had their information stolen.

Experian said it immediately notified law enforcement authorities after discovering the hack and that ‘there is no evidence to date that the data has been used inappropriately’.

T-Mobile customers can sign up for two free years of credit monitoring services at www.protectmyID.com/securityincident, a service owned by Experian.

That arrangement prompted sarcastic responses on Twitter. T-Mobile CEO John Legere, who is active on Twitter, responded to many tweeters unhappy with the resolution offered.

“I hear you re: Experian as service protection option. I am moving as fast as possible to get an alternate option in place by tomorrow,” Legere wrote on Thursday evening.

Earlier in a statement, Legere had said that he was ‘incredibly angry’ about the breach and that the company would review its relationship with Experian.

‘Customers will be cynical’ about using credit monitoring from Experian, said Avivah Litan, a Gartner security analyst. “Why would you trust someone with your accounts that’s been breached.”

Still, she said that customers can still use the service. But as an alternative, they could check their credit reports for free at www.annualcreditreport.com. The site lets consumers check each of their credit reports from the three credit rating agencies — Equifax, Experian and TransUnion — once a year.

The hack happened on Experian’s server and is still being investigated, said Annie Garrigan, a spokeswoman for Bellevue, Washington-based T-Mobile.

Experian said in a statement on its website that it doesn’t know who was behind the hack and that it is taking ‘necessary steps’ to prevent further breaches.

The firm said affected customers should ‘remain vigilant’ against identity theft and watch for phishing e-mail scams that ask for sensitive information.