What type of cyberattack was discussed in the Ukrainian power grid case study?

The Ukrainian power grid cyberattack (2015 and 2016 incidents) is widely documented as a “nation state” attack. It was attributed to a highly skilled, well-resourced group with nation-state backing, and demonstrated the ability to compromise, disrupt, and remotely control industrial systems in critical infrastructure. This attack is discussed in ISA/IEC 62443 training and guidance as an example of advanced persistent threat (APT) activity targeting industrial control systems.