Personal data describing 1.3 million customers of Orange France has been stolen in the second hack to hit the telco this year.
Hackers made off with subscriber names, dates of birth and phone numbers of about 4.9 percent of the telco's subscriber base.
The company said hackers accessed data used for its email and SMS marketing campaigns but did not disclose how the April 18 breach was executed.
It took the almost three weeks since the breach to probe for vulnerabilities and analyse the extent of stolen data.
In a statement (French) the telco said the stolen data could be used to phish subscribers using email, SMS and phone calls.
Customers took to the telco's Facebook page to express anger over the breach with some receiving phishing emails relating to bounced invoice payments.
Orange France confirmed it did not ask for bank details via email or SMS but it was unclear if the phish was related to the breach.
The hack came a little over two months after 800,000 customer details were stolen by hackers raiding the telco's 'My Account' page. Crims made off with names, email and street addresses, customer IDs, and phone numbers.
In September, hackers attacked Vodafone Germany and made off with names, addresses and bank details of two million subscribers.®