Recently there was a thread on SCADASEC news, a restricted access critical infrastructure mailing list, about the challenges of firewalling BACnet networks. If you only work in the industrial automation space, you may not have heard of this protocol, but it is big in building automation. Regardless, the discussion around BACnet applies to many industrial protocols.

The question raised was whether or not BACnet traffic can be managed by a firewall. The problem is that BACnet, like many other automation protocols, doesn’t play by the usual IT rules. In BACnet’s case, it does not use TCP/IP at all, so trying to secure it with a typical IT firewall that looks for TCP port numbers is a lost cause.


BACnet is a non-TCP /IP protocol used in building automation systems that cannot be secured by typical IT firewalls. Image courtesy of Schneider Electric.

Furthermore, the point was raised that if a security device has the ability to secure BACnet, it would be so complicated that an industrial engineer could not manage it. And, if you get the IT “security guru” involved then you create a reliability nightmare. So SCADASEC contributors asked “Can a non-TCP/IP industrial network be realistically secured?”

Several people in the SCADASEC discussion independently brought forward that the Tofino Industrial Security Solution can secure BACnet and do it easily. It was nice to read how these products, which are part of Belden’s industrial networking solutions, can be used in ways we haven’t even tried yet. For example:


The SCADASEC thread on securing the BACnet indicates the Tofino Firewall does the job nicely.
Thread presented here with permission.
Which brings up an interesting point, how is it that engineers in the field know that Tofino can handle protocols that we don’t? The answer is that if you design a product to both meet the needs of a specific environment and yet be flexible, then the users will find all sorts of ingenious ways to use it that the designers never imagine.

It turns out that to really work on the plant floor (or building site), an industrial cyber security solution must be:

1. Capable of reliably securing industrial protocols as they exist in the real world (not in an ideal world)

2. Easily configurable by a controls technician, yet extensible to handle unusual situations

1. Designed for How Industrial Networks are used in the Real World

In order to protect manufacturing processes, an industrial firewall needs built-in smarts for understanding some unusual protocols. Industrial protocols emerged in the 1970’s and they were designed to provide data from PLCs, DCS and other devices to help monitor processes and make them as efficient as possible. They were not designed with security in mind. Nor were they designed to operate like IT networks. They had a job to do and the designers focused on making sure that the system worked “good enough” to safely make product.

The result wasn’t always pretty when looked at closely. It was not always to the letter of the specifications. Nor did these industrial protocols bother with a lot of the IT expectations of what a network should do. For example, who needs to manage wide area routing if your network is going to stay inside a building?

Thus extras like a TCP/IP layer got removed from industrial protocols like BACnet and GOOSE. And features like robust authentication were left out of nearly all the industrial protocols. After all, who would ever want to hack a control system?

Now twenty years later things have changed. Industrial networks do extend outside a single building. And (unfortunately) people do want to hack a control system and cause trouble. However the equipment and protocols have not. Modbus is still basically the same protocol it was when it was specified in the ‘70s. BACnet is much the same as it was in1989.

This means that any industrial security system has to offer the flexibility to work with some unusual networks. The BACnet case is a perfect example.

2. SCADA Security that a Control Engineer can Configure

Industrial security needs to be simple in order to be effective. Highly complex and cumbersome configuration, as required by some IT firewalls just does not work in facilities staffed by engineers, technicians and maintenance people.

Using a product with a graphical interface, terminology and templates that make sense to them, control specialists can build traffic rules using terms and concepts that are familiar to them. For example, most engineers that use Rockwell control products do not have any idea what CIP objects and services are flowing over their network. The system just works.

They might not even know what TCP and UDP port numbers their PLC to HMI traffic uses. But they do know that they want EtherNet/IP messages to go from a PLC to an HMI so they can read a set of Analog Values.

So the answer is to have the firewall configuration displayed in terms that make sense to the engineer, not the creator of the protocols. Replace “TCP Port 44818” with “EtherNet/IP (CIP) Explicit Msg” in the software. Replace “CIP Object Class ID 0x28” with “Motor Data Object”. And replace a mess of different ODVA Services with “Read data”.

Ethernet-IP-Rule-Details The Tofino Firewall makes it easy for controls engineers to configure rules that secure industrial protocols.

But even with the easiest to understand screens and wizards, mistakes can be made. So once rules are created, engineers can then safely try them out in “test mode”. This makes sure the rules are correct for the process without any risk of accidentally blocking communications that are critical to plant operation.

The Tofino Firewall also provides pre-defined templates for over 25 families of popular industrial controllers, including rule definitions to protect devices with known vulnerabilities.

In addition to pre-defined templates, Tofino Security firewalls can be extended using a Special Rules feature where rules can be developed and be applied to “unusual” protocols like BACnet.

Securing Industrial Protocols – It Can be Done

I hope this article gives you a sense of how current industrial security technology can truly secure manufacturing networks. If you want to read the SCADASEC thread yourself, register to become part of the mailing list and then go to its archives and search on BACnet.

If you have tips or remarks you would like to share regarding securing difficult industrial protocols, please let me know.

This article is a collaboration between Heather MacKenzie and Eric Byres.

Related Links

Webpage: SCADASEC Mailing List
Blog: SCADA Security Basics: Why are PLCs so Insecure?
Blog: S4 SCADA Security Symposium Takeaway: Time for a Revolution
Blog: Securing SCADA systems from APTs like Flame and Stuxnet – Part 1
Blog: Patching for SCADA and ICS Security: The Good, the Bad and the Ugly
Blog: Securing SCADA Systems: Why Choose Compensating Controls?
Webpage: Tofino Modbus TCP Enforcer LSM
Webpage: Tofino Firewall LSM
Webpage: Tofino Security Appliance