Stuxnet Worm, Research and Recommendations
As you may be aware, a worm (originally appearing in 2009) and named Stuxnet has recently resurfaced as a focused attack at Industrial and Energy control systems, namely but not exclusively targeting those systems built by Siemens, AG. This worm has the capability to take control of and/or alter settings within SCADA systems and PLC/RTU sub-components.
Below are some good articles related to recent research into the worm.