The German media group Südwestdeutsche Medienholding (SWMH), which owns the daily Süddeutsche Zeitung, among other publications, has been the target of a "critical IT security incident," it said on Tuesday.

The group said its internal network was briefly accessed by unauthorized individuals in mid-July, affecting all the companies connected by it, including the Stuttgarter Zeitung and Stuttgarter Nachrichten dailies.

It said the attack had been stopped and that all online reporting and newspaper production had continued without disruption.

Cybercrime investigation underway

The group detected the first signs of unusual activity over the weekend of July 12-13.

By the start of the week, extensive security measures had been taken to stymie the attack. 

The attack has been reported to the police cybercrime unit and the incident is also being investigated by external IT security experts, it said.

The group said it was cooperating closely with law enforcement and data protection authorities as they work to identify the individual or individuals behind the attack and to enhance cybersecurity.

Germany has experienced a growing number of cyberattacks on both private companies and government organizations over the past few years.

Many have been blamed on Russia or China.

SWMH is one of Germany's largest newspaper publishers and employs some 4,500 people.

Edited by: Elizabeth Schumacher