Securing connectivity in operational technology (OT) environments is crucial for the safety of critical infrastructure and maintaining the uninterrupted service it provides. Leaving unnecessary open ports, protocols, and services exposed, along with directly connected devices to the internet, such as programmable logic controllers (PLCs) and human machine interfaces (HMIs), greatly increases the risks of cyberattacks. These vulnerabilities can lead to severe operational disruptions, substantial financial losses, threats to human life, and lasting environmental harm.
Organizations should fortify their remote connectivity against potential threats and enable employees and/or contractors to access control systems securely. This includes implementing well-configured security measures such as virtual private networks (VPNs) and jump boxes and maintaining continuous vigilance through monitoring and proactive updates to security protocols. Dynamic approaches are crucial to addressing the evolving cyber threat landscape.
Insecure connectivity in OT environments refers to vulnerabilities created through poorly designed control system devices, misconfigurations of these devices, and flat network architecture that exposes critical systems to potential cyber threats. Examples include an open web server (HTTP port 80) on a PLC that attackers can exploit to gain unauthorized access, or open, vulnerable ports on PLCs and/or HMIs directly connected to the internet, making them accessible to malicious actors.
Such exposures increase the risk of cyberattacks and operational disruptions and compromise the safety of industrial control systems (ICS). A lack of proper network segmentation can also spread malware across connected devices or enable attackers to pivot from business IT to OT networks. Additionally, outdated or improperly configured security services (e.g., weak encryption) can leave systems to be exploited. Addressing these vulnerabilities underscores the necessity of establishing robust security processes and procedures to safeguard OT environments against potential hazards.
The risks associated with cyberattacks on OT systems are significant and can lead to physical damage, disrupt critical infrastructure, and endanger human lives. For instance, attackers exploiting vulnerabilities in PLCs or HMIs may manipulate industrial processes, causing equipment failure or catastrophic accidents. Misconfigured or poorly secured connectivity in OT potentially exposes sensitive operational information, resulting in intellectual property theft and competitive disadvantages.
Such cyber incidents can also cause significant financial setbacks by interrupting operations, resulting in production stoppages and downtime. Furthermore, compromised systems can erode stakeholder trust and damage an organization's reputation, while the spread of malware across both OT and IT networks amplifies the threat landscape.
Several incidents highlight the tangible dangers of insecure connectivity in OT environments. In 2015, Ukraine's power grid was attacked, and one of the components that enabled this attack was the VPNs into the ICS from the business network that did not have two‐factor authentication. The insecure VPN and the firewall configuration allowed the attacker to set up access in the unmonitored OT network using native remote access software to discover the remainder of the systems and extract data necessary to formulate a plan that eventually caused widespread power outages affecting hundreds of thousands.
A 2020 attack on a natural gas facility led to operational shutdowns when ransomware infiltrated IT and OT systems due to a lack of network segmentation. In November 2023, Iranian Government Islamic Revolutionary Guard Corps (IRGC)- affiliated Advanced Persistent Threat (APT) cyber actors compromised a public-facing PLC on the internet with a default administrative password at a water treatment plant. This allowed the attackers to alter the HMI display and hinder access to the PLC, potentially jeopardizing the water treatment facilities' capacity to deliver clean drinking water and efficiently handle wastewater for their community.
Secure connectivity alternatives are not just a choice but necessary for protecting OT environments from cyber threats. These solutions, including VPNs, jump boxes, and other secure methods like network segmentation, provide practical ways to shield OT networks from unauthorized access. VPNs, for instance, create encrypted tunnels over public networks, ensuring that data transmitted between remote users and OT systems remain confidential and tamper-proof. On the other hand, Jump boxes act as controlled gateways between external networks and critical OT systems, requiring users to authenticate before accessing sensitive devices like PLCs and HMIs. Other secure methods involve firewalls, Intrusion detection systems (IDS), and robust authentication protocols to enhance OT network security further.
The pros and cons of VPNs and jump boxes highlight the considerations in choosing the appropriate solution. VPNs offer the advantage of secure remote access, enabling personnel to connect to OT systems from anywhere, and encryption safeguards the data. However, VPNs can be complex to configure correctly, and misconfigurations may create vulnerabilities that attackers can exploit. They also require constant updates and monitoring to maintain security. Jump boxes reduce the attack surface by limiting direct access to OT devices and allowing for centralized user activity monitoring. The downside is that if a jump box is compromised, it can serve as a single point of failure, granting attackers access to critical systems. While secure methods like strict network segmentation or zero-trust models operate on the principle that no connection is inherently trusted, VPNs and jump boxes offer practical solutions but require careful management. Ultimately, the most secure strategy may be a blend of these techniques, customized to fit the unique demands and threats of the OT environment.
Implementing best practices for ensuring secure connectivity in OT environments involves several critical steps to mitigate risks and enhance security. Organizations can proactively address potential threats and reduce the likelihood of exploits by conducting comprehensive risk assessments to identify vulnerabilities within their OT networks.
Simply evaluating and disabling unnecessary ports and protocols in OT can minimize exposure to cyber exploitation and attacks. Implementing network segmentation is crucial; by isolating OT systems from IT networks and employing demilitarized zones (DMZs), organizations can limit the spread of potential attacks and protect critical systems. Deploying robust authentication mechanisms such as multifactor authentication (MFA) and role-based access control ensures that only authorized personnel can access critical systems, reducing the risk of unauthorized access and potential damage. Additionally, regularly updating and patching systems while challenging in OT due to potential downtime helps protect against known vulnerabilities and ensures the system's resilience. Encryption and secure communication protocols safeguard data in transit between devices and control centers, maintaining the confidentiality and integrity of the data.
Ensuring continuous monitoring and maintaining security updates or upgrades cannot be overstated. Implementing IDS enables real-time detection and response to malicious activities within the network. Regular security audits and vulnerability assessments help organizations avoid emerging threats and ensure compliance with industry standards. Employee training and awareness programs are vital, as human error can be a significant risk factor in OT security. Maintaining an up-to-date incident response plan enables organizations to respond quickly and effectively to security incidents, minimizing potential damage. By continuously monitoring networks and updating security protocols, organizations can adapt to evolving cyber threats and better protect their OT environments.
Securing connectivity in OT environments is essential for the safety and reliability of critical infrastructure. Insecure connections—such as open ports and direct internet access to PLCs and HMIs, expose systems to significant risks like cyberattacks, data breaches, and operational disruptions. Real-world incidents, including the attacks on Ukraine's power grid, natural gas facility, and water treatment plant, underscore the impact of such vulnerabilities. Organizations can effectively mitigate these threats and protect their operations by recognizing these common weaknesses, implementing secure connectivity alternatives like Virtual Private Networks (VPNs) and jump boxes, disabling unnecessary ports, protocols, and services, and enforcing network segmentation.
Organizations need to enhance OT security proactively. Implementing best practices such as conducting comprehensive risk assessments, adopting secure communication protocols, and continuously monitoring and updating security measures is essential. Providing employee and/or contractor training ensures your team recognizes potential threats and fully grasps their responsibility in maintaining security. By fostering a culture of vigilance and prioritizing cybersecurity, organizations can safeguard their OT environments against evolving threats. By staying dedicated to this cause, we protect valuable assets and data and ensure the safety and well-being of the communities that depend on these essential systems.
Dan Ricci is founder of the ICS Advisory Project, an open-source project to provide DHS CISA ICS Advisories data visualized as a dashboard to support vulnerability analysis for the OT/ICS community. He retired from the U.S. Navy after serving 21 years in the information warfare community.
