Swiss telecoms giant Swisscom on Wednesday said it had tightened security controls after suffering a data breach that affected roughly 800,000 of its customers.

The company said unauthorized parties gained access to customer data by leveraging the access privileges of a sales partner. The attackers somehow obtained the partner’s credentials and used them to access contact information, including names, physical addresses, phone numbers, and dates of birth.

Swisscom pointed out that it collects this type of data legally from customers when they enter a subscription agreement, and sales partners are given limited access to records for identification and contracting purposes.

The company noted that this type of information is not considered sensitive under data protection laws, and it’s mostly either already in the public domain or in the hands of list brokers.

The data breach has affected approximately 800,000 Swisscom customers, mostly mobile services subscribers. The company said it had detected the incident during a routine check, but an in-depth investigation was launched following its discovery.

“Swisscom stresses that the system was not hacked and no sensitive data, such as passwords, conversation or payment data, was affected by the incident,” Swisscom stated. “Rigorous long-established security mechanisms are already in place in this case.”

While the compromised data is non-sensitive, Swisscom has reported the incident to the Swiss Federal Data Protection and Information Commissioner (FDPIC).

In response to the breach, the company has revoked access for the firm whose credentials were stolen and implemented tighter controls for partners. In the future, Swisscom wants to ensure that high-volume queries for customer information can no longer be run, and introduce two-factor authentication for sales partners when accessing its systems.

The company says it is not aware of any schemes leveraging the stolen data, but it has advised customers to be wary of any suspicious calls.

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