The attack used spear phishing and sophisticated social engineering techniques to gain access to the factory’s office networks, from which access to production networks was gained. Spear phishing involves the use of email that appears to come from within an organisation. After the system was compromised, individual components or even entire systems started to fail frequently.

One of the plant’s blast furnaces could not be shut down in a controlled manner, which resulted in “massive damage to plant,” the BSI said, describing the technical skills of the attacker as “very advanced.”