From https://www.fireeye.com/blog/threat-research/2017/12/attacke...

>The targeting of critical infrastructure to disrupt, degrade, or destroy systems is consistent with numerous attack and reconnaissance activities carried out globally by Russian, Iranian, North Korean, U.S., and Israeli nation state actors. Intrusions of this nature do not necessarily indicate an immediate intent to disrupt targeted systems, and may be preparation for a contingency.

This reeks of Stuxnet 2.0