ICS and SCADA Security Myth: Protection by Firewalls

(This article was originally published in the June, 2012 ICSJWG Quarterly Newsletter.) In this article I am going to talk about a fairy tale. This tale doesn’t have princes or frogs in it, but instead it deals with SCADA and industrial control system security. The existence of a “firewall” between control system networks and the rest of the world has been one of the most enduring fairy tales in the field of SCADA/ICS security. The idea is that, in a properly designed system, there is a logical barrier between the control network and the business network. Since unauthorized information cannot cross such a firewall, bad things like hackers and worms can never get into critical control systems. From this, a corollary flows: