Personal details of UPC Polska subscribers have been made offered for sale online by hackers.
In a statement, the Polish operator says its security experts have now blocked access to the information and are monitoring the situation.
It adds that access to the details would have been obtained through login and password details used by someone cooperating with the company.
In accordance with the law, UPC Polska is now informing the General Inspector, its subscribers – 36 were affected in this instance ¬– and law enforcement.
At the same time, it is undertaking its own intensive investigation in order to establish how the leak came about and to ensure something similar does not happen in the future.