Are Viruses a Reason for Concern?

This is a flawed question. None of the facilities I have worked at or designed are internet accessible. In fact, the vast majority of the vital infrastructure facilities in the US are not networked.

But don't take my word for it. Dig up the information for yourself. Here's a start.

http://www.infowars.com/cybersecurity-lie-exposed-power-plants-are-not-connected-to-the-internet/

You simply aren't going to be able to jump on your pc, type some IP address and pull up controls to a power company... yet.

I would repose the question to something like, "What benefit do facilities have by implementing internet capable controls (such as some parts of the smart grid technology) that outweigh the costs of the added security risks?"

Perhaps there are a few, remote operated plants out there that could answer your question directly as stated. But, so far, my firm has had ZERO requests to design or integrate any plants with the internet.