Seen on Netcom-Kassel (translation):
Information according to Paragraph 109a TKG, 34 GDPR on a security incident (status: 05.02.2021)
On Monday, January 18, 2021, the Netcom Kassel Gesellschaft für Telekommunikation mbH was the target of a hacker attack.
Some of the general IT systems were affected by the attack, which is why they are currently only available to a limited extent. The systems for network operation (telephone and Internet services) are not affected.
Read more on Netcom Kassel.
h/t, @Chum1ng0