If you have had the chance to walk around a power plant, manufacturing plant or any other plant of size, you likely experienced very little attention once you are through the front gate. If you have a hard hat and safety shoes you can walk almost anywhere with a look of confidence. And so many contractors come in and out of the plant that getting in is often not at all difficult.
So assuming you have physical access, check out the Pwn Plug from Pwnie Express. Plug it into power and an Ethernet port with DHCP, and an attacker has created a backdoor that can be used at his leisure. Takes less than 15 seconds to install.
Spend a couple of $100 more and you get mobile wireless network access so you don’t even need to be nearby. The elite model is preloaded with many security tools. There is even support for Zigbee now so you can remotely attack the wireless plant network, although Wireless HART and ISA 100 thankfully have some security.
Note – This isn’t news if you follow IT security, but it probably is new to many in the ICS world.