The servers that were subject to the attack were thought to be absolutely protected in terms of potential external attacks, the news outlet added.
Later, German Interior Ministry spokesman Johannes Dimroth said that the situation after the cyberattack was "restrained and taken under control."
"We attach great importance to what happened, and we are using all available resources," Dimroth said, as quoted by Focus magazine. He stressed that the investigation of the incident was underway.
The Fancy Bears group is thought to be allegedly linked to Russia by a number of states, however, these claims have never been proven. The group is best known for its attack on the World Anti-Doping Agency (WADA) which resulted in a leakage of documents proving that a number of prominent athletes such as tennis players Rafael Nadal, Venus and Serena Williams, as well as artistic gymnast Simone Biles, used banned drugs under the Therapeutic Use Exemptions program.
News agency reported that the hacking activities targeted such companies as Lockheed Martin Corp., Raytheon Co., Boeing Co., Airbus Group and General Atomics, as well as small companies.
The media outlet also reported that the information about the phishing attacks had been collected by the cybersecurity company Secureworks in the period between March 2015 to May 2016.