Keeping industrial facilities safe – the importance of network segregation

Industrial environments can pose many risks. The majority of facilities require the use of specialist equipment on a daily basis and in some sectors, such as Nuclear, that equipment often controls hazardous products. The loss of function or manipulation of such technologies could therefore be devastating, leading to equipment damage, or even human fatalities. This loss of function could be administered by cyber criminals, and while their motivations for targeting such environments vary, it is important for those organisations in charge of critical infrastructures to understand that they are now under constant threat, and that they should be putting security measures in place to protect themselves against such attacks.

The importance of Safety Instrumented Systems (SIS)

Safety Instrumented Systems (SIS) are considered as the last layer of defence in an industrial facility, assuring an industrial process can be maintained within safe operating limits with fail-safe protection. To ensure this fail-safe protection is effective, SISs were originally designed utilising hardwired analogue systems and manual processes. However, with the continued advancement of networking and sensor technologies, alongside the convergence of control system platforms, many SISs are no longer isolated, instead using standard networking technologies.

The problem this often creates is that a lack of segregation can effectively introduce a “back-door” into the safety network, meaning sophisticated attacks are able to compromise automatic safety systems. The most recent example of this is the new Industrial Control Systems (ICS) attack framework TRITON, built to interact with Triconex SIS controllers[1].


Figure - Integrated Control and SIS Architecture

A new threat to Safety Instrumented Systems (SIS)

The TRITON attack, first identified in late 2017, targeted critical infrastructure, compromising ICS and deploying malware designed to manipulate SISs and shut down industrial processes. While it is not clear who carried out the attack, researchers suggest that it was “consistent with numerous attack and reconnaissance activities carried out globally by Russian, Iranian, North Korean, U.S., and Israeli nation state actors[2].” The concern is that TRITON could prevent safety mechanisms from performing their intended function which, if carried out again, could result in devastating physical consequences.

The attack was made possible as the threat-actors could target SISs connected to the network. In order to mitigate such future threats it is recommended that, where possible, safety system networks are segregated from Basic Process Control Systems (BPCS) and information system networks. We would also suggest those organisations in charge of critical national infrastructures implement a comprehensive cyber security program. This should be designed to identify what assets need to be protected, the threats to those assets, what could happen if those assets were breached, and how to ensure recovery should an incident occur.

Applied Risk recommends the following steps to ensure that safety systems are protected appropriately

  • 1.Identify the SIS which your organisation operates, and document whether or not the SIS is isolated from the rest of the control system.
  • 2.Validate whether the SIS provides a mechanism which prevents re-programming or network access to the device during operation. If this feature is available, then visually verify the position of the key switch of the devices to ensure they are switched to 'run-mode' or equivalent.
  • 3.Verify that the network is segregated properly (both vertically and horizontally) and that no trusts exist with other Active Directories or shared IP Telephony network (which is likely to be a target of compromise).
  • 4.Ensure that any components which connect to the ICS from the corporate network are strongly authenticated and consider using 'browse-down' techniques to prevent exploitation of critical systems. Review authentication, authorisation and access control mechanisms for OT devices.
  • 5.Restrict access for end user devices and critical systems in the ICS environments. SIS administration systems such as engineering workstation should not have internet access (e.g. email/browsing)..
  • 6.Only modern and patched components should be deployed on the boundaries of OT networks, and software deployed to SIS environments should be validated with the vendor using a suitable security mechanisms.
  • 7.Consider monitoring ICS network traffic for unexpected communication flows and other anomalous activity.

A cybersecurity Risk and Vulnerability Assessment will help identify risks in your Safety Instrumented Systems implementation. Discover Applied Risk’s RVA solution here.