Reuters is reporting that nuclear is being targeted by a hacking campaign. The article is exceedingly ambiguous and truncated and simply indicates that the US Dept of Homeland Security and FBI warned businesses across sectors of a hacking campaign aimed at "harvesting credentials":
Jim Finkle (2017, June 30). U.S. warns businesses of hacking campaign against nuclear, energy firms. Reuters, http://www.reuters.com/article/us-usa-cyber-energy-idUSKBN19L2Z9I had thought US nuclear plants weren't connected directly to the Internet and therefore were not susceptible to external system hacks. Seems that is not quite true because nuclear "control" systems are apparently connected and vulnerable
Hackers used tainted "phishing" emails to "harvest credentials" so they could gain access to networks of their targets, the joint analysis report seen by Reuters late on Friday said.
Chris Shipp and Jonathan Pollet (February 3, 2015). Hacking control systems are not immune. Valve Magazone, http://www.valvemagazine.com/magazine/sections/features/6480-hacking-control-systems-are-not-immune.html
In January 2003, computers at the Davis-Besse nuclear power plant were infected with the Slammer worm2—a piece of malicious code that spread faster than any before or since. This particular infection is noteworthy for two reasons:
First, the code was only able to spread because computer owners did not apply security patches in a timely manner. (Microsoft had released a security patch to mitigate the vulnerability six months before Slammer began its historical spread).
Second, during the ensuing investigation, personnel at the plant indicated they thought they were protected from such attacks because they had a firewall. Unfortunately, this lack of understanding with respect to cybersecurity is still prevalent—especially in the control system community.