AT&T, the American telecoms giant, has confirmed that personal data from around 7.6 million account holders and 65.4 million former customers has been leaked on the dark web.

The information involved may have included full names, email addresses, mailing addresses, phone numbers, social security numbers, dates of birth, and AT&T account numbers and passcodes.

Personal financial information and call history doesn’t appear to be included, said the company.

Following the firm’s preliminary investigation, the data set that’s been published on the dark web appears to be from 2019 or earlier.

It’s not yet known if the data in the data set originated from AT&T, or a third-party supplier. The company said that it currently “does not have evidence of unauthorized access to its systems resulting in theft of the data set.”

In response, the telecoms giant has taken “precautionary measures” and reset customer passcodes – a numerical PIN to add an extra security layer to AT&T accounts, and is separate from regular passwords.

AT&T said that it will be contacting individuals with compromised sensitive personal information via email or mail, and providing identity theft and credit monitoring services.

It’s meanwhile advising customers to “remain vigilant by monitoring account activity and credit reports.”

“You can set up free fraud alerts from nationwide credit bureaus — Equifax, Experian, and TransUnion. You can also request and review your free credit report at any time via Freecreditreport.com,” it encouraged.

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This isn’t the first time AT&T has been in the news this year. In late February, service disruption led to an outage in the US, with the company offering $5 credit to customers affected.

In an update amid the disruption, the company said that “we believe that today’s outage was caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack.”

AT&T’s mobile network provides coverage for more than 240 million customers across the US.