The telecom firm made the disclosure as an extortion group reportedly claimed Frontier as a data theft victim.

Frontier Communications revealed that a previously disclosed cyberattack, which occurred in mid-April, exposed the data of more than 750,000 customers.

The Dallas-based telecom firm made the disclosure as an extortion group reportedly claimed Frontier as a data theft victim.

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In a disclosure posted by the Maine attorney general website, Frontier said the data could include names and Social Security numbers of customers, and affects a total of 751,895 customers.

The attack was detected April 14 and prompted the company to take “containment measures, which included shutting down certain of the company’s systems,” Frontier said in a previous filing with the U.S. Securities and Exchange Commission.

This action “resulted in an operational disruption that could be considered material,” the company said.

Meanwhile, multiple media reports indicated that a data extortion group, RansomHub, has posted Frontier as one of its victims on its dark web site.

The group claims that it will sell 5 GB of data belonging to 2 million customers unless Frontier responds to its demands by June 14, according to a BleepingComputer report.

CRN has reached out to Frontier for comment.