An online attack on a German steelworks caused massive damage to the infrastructure, according to reports.

The incident marks “one of the rare instances in which a digital attack actually caused physical damage”, reported IT World.

Beginning with a targeted spearfishing attack the unknown hackers managed to gain access to the factory's internal systems, using fake emails which appeared to come from within the organization to trick staff into installing malware, according to The Telegraph.

Once this malicious code was installed on computers at the plant, staff noticed that systems and components began breaking down increasingly regularity. Due to these failures, one of the plant’s blast furnaces could not be shut down in a controlled manner, which resulted in “massive damage to plant,” the German Federal Office for Information Security (BSI) said in an official report, which goes on to describe the technical skills of the attacker(s) as “very advanced.”

IT World continued: “The attack involved the compromise of a variety of different internal systems and industrial components, BSI said, noting that not only was there evidence of a strong knowledge of IT security but also extended know-how of the industrial control and production process.”

However, this German steelmill is not the first facility to be seriously damaged by a purely digital attack – the Stuxnet worm crippled an estimated 1,000 of 5,000 uranium centrifuges inside Iran’s Natanz uranium enrichment facility by spinning them at destructive speeds in 2010.