After the hacker attack on the Hessian IT service provider Count and Care, cybercriminals published a large amount of personal data on customers, employees and business partners of the energy supplier Entega on the dark web.
Entega AG, whose subsidiary Count and Care is, announced on Wednesday that it was primarily names, addresses and consumption data, but in some cases also bank details.
"According to the current state of knowledge, the criminal publication of the data affects a large number of customers of Entega and its subsidiaries."
The Darknet is a network within the Internet that can only be accessed with special software and is intended to offer extensive anonymity.
It is used, for example, by activists in authoritarian countries - but also by criminals for illegal business.
It is unclear who is behind the cyber attack in mid-June.
It was previously known that the criminals were using so-called ransomware, a type of malware.
With such a program, computers can be encrypted and thus access to data and systems can be restricted or even completely prevented.
The attackers demand a ransom for the decryption.