Wired had an article a while ago (January 6th 2014)
To understand the problem, you need to understand the embedded systems market.
The problem is the chip manufacturers make custom devices with custom parameters, that frequently have exploitable services. And they do not get patched, since no one tests them.
We have found viruses on these machines. And the only way to fix is either disconnect from internet or wait for the manufacturer to provide a fix. This fix may take months.
You must test your whole environment, not just the known network devices. Since someone may have plugged in an appliance which becomes vulnerable with easy to use hacker programs.
Use our Solutions page to help you decide how we can help.