The Local.de reported the cyberattacks led 50,000 students in western Germany to change email passwords after a recommendation from the university.
Authorities traced the hackers' IP address to Russia but it wasn't clear whether the owners of the computers were responsible for the attacks.
Authorities said what the hackers were after also was unclear.
'How to Train Your Dragon 2' releases 5-minute clip
Lytro unveils camera that can focus a photo after shooting it