The Ultimate Guide to PLC Cybersecurity

Apr 19, 2024

Blog-The Ultimate Guide to PLC Cybersecurity

PLCs Can Leave OT Networks Vulnerable to Attack

In today’s OT threat environment, PLCs — Programmable Logic Controllers — have become one more attack surface for threat actors looking for easy entry points to industrial facilities.

PLCs are inviting targets for a number of reasons, including the fact that many have been in service for decades, built before OT security was even a notion, and thus lack any built-in secure protocols. Today, with PLCs being much more connected to business systems and wireless networks, the lack of security measures is a growing threat to industrial environments.

Within organizations, amid a general lack of understanding of OT security, operations managers and IT-focused security teams are unlikely to appreciate all the specific exposure that PLCs create. There’s even a shortage of OT security awareness among the builders and coders of modern PLCs.

The limited availability of purpose-built tools to secure PLCs has also been a problem, but that is starting to change. So is the approach to OT security overall, as it becomes a growing and publicized concern, and as the attacks on OT networks have become more aggressive and damaging.

Fortunately, there are effective and immediate steps you can take to provide real security for PLCs.


PLC Cybersecurity

Protecting PLCs is essential to safeguarding critical infrastructure from potential cyber threats. PLCs are highly susceptible to cyberattacks, which, if successful, could lead to severe consequences like disrupting operations or compromising human safety.

Security measures for PLCs should include standard methods, such as robust access controls. However, many standard recommendations for IT, such as strong encryption, are difficult to implement in the OT environment. OT also makes regular software updates impractical, if not impossible, since it can mean shutting down production.

A viable alternative is virtual patching, putting an in-line IPS (intrusion prevention system) in front of these systems and segmenting the networks to isolate them, accomplishing the same goals as standard patching.

Modern, effective cybersecurity strategy will also involve elements such as continuous monitoring, the integration of threat intelligence, and employee training. These measures are crucial for ensuring the protection of PLCs and, consequently, safeguarding the critical industrial processes under their control.


A Brief History of PLCs

Technological advancements and industry demands have been the main driver behind the evolution of PLCs. PLCs originated in the late 1960s, beginning as relay-based control systems. PLCs then rapidly evolved with the advent of microprocessors in the 1970s. The integration of microprocessors allowed for increased programmability, enabling PLCs to replace traditional relay logic systems as a more flexible option better suited for industrial automation.

The 1980s witnessed the adoption of modular and rack-mounted PLCs, providing scalability and modularity to suit diverse applications. As the 1990s unfolded, PLCs incorporated networking capabilities, paving the way for enhanced communication between devices, especially integration with Supervisory Control and Data Acquisition (SCADA) systems. The 21st century saw PLCs embracing Industry 4.0 principles, integrating with the Internet of Things (IoT) and cloud computing for real-time monitoring and data analysis. (These, of course, are some of the reasons they are more vulnerable today.)

Today’s PLCs are characterized by their enhanced capabilities, high processing power, and advanced features like artificial intelligence and machine learning integration, supplying unparalleled control compared to previous generations of PLCs. This evolution reflects the continual adaptation to technological trends and the ever-growing demands of modern industrial processes.


Why PLC Cybersecurity Matters

PLC cybersecurity is crucial as industrial systems increasingly rely on interconnected networks. A breach in Programmable Logic Controllers could lead to devastating consequences, including production shutdowns, safety hazards, and economic losses.

Protecting PLCs ensures the integrity of critical infrastructure, safeguards against unauthorized access and manipulation, and prevents potential cascading effects on industrial operations and, in some cases, public safety. As industries become more digitized, prioritizing PLC cybersecurity becomes paramount in mitigating risks and maintaining the reliability of essential processes.


The Stuxnet Attack

The Stuxnet PLC attack, which occurred in 2010, was a watershed moment for cyber warfare. Widely attributed to joint efforts by the United States and Israel, Stuxnet targeted Iran’s nuclear facilities, specifically its uranium enrichment program.

The sophisticated malware exploited zero-day vulnerabilities in Windows operating systems to infiltrate industrial control systems, particularly Siemens’ Programmable Logic Controllers. Stuxnet covertly manipulated the PLCs, causing centrifuges to spin at erratic speeds, which ultimately sabotaged Iran’s nuclear ambitions (without overtly causing any physical destruction).

The Stuxnet attack demonstrated the power and potential of cyber weaponry, blending espionage, sabotage, and precision targeting, all within the digital realm. Its discovery underscored the vulnerability of critical infrastructure to cyber threats and spurred increased global awareness regarding the need for robust cybersecurity measures in industrial control systems.



The TRITON/TRISIS attack, discovered in 2017, marked a significant escalation in cyber threats targeting industrial control systems. Aimed at a petrochemical plant in the Middle East, the malware, also known as TRISIS, specifically targeted Schneider Electric’s Triconex Safety Instrumented System (SIS).

Unlike previous cyber incidents, TRITON was designed not just for espionage or disruption but to manipulate the plant’s safety systems, posing severe physical risks. The attackers sought to disable the Triconex SIS, a crucial component ensuring the safe operation of industrial processes.

The unprecedented attack raised alarms globally, emphasizing the potentially catastrophic consequences of compromised safety systems. The TRITON incident underscored the urgent need for heightened cybersecurity measures in critical infrastructure, urging organizations worldwide to reevaluate their defense strategies against increasingly sophisticated threats to industrial control systems.


How to Navigate Advanced PLC Security Measures

Successfully navigating advanced security measures for a PLC system requires a multifaceted approach. Implementing robust access control and restricting system entry to authorized personnel are vital for shielding the PLC from potential cyber threats.

Traditionally, PLC security is classified into three major categories:

1) Threat Detection and Prevention

2) Secure Communication Protocols

3) Access Control and Authentication

Best practices should include a thorough risk assessment to identify potential weaknesses. Continuous employee training is also important. While a lack of internal resources can be an issue, there are third-party vendors to work with. Measures should also incorporate anomaly detection systems for real-time monitoring. And it’s important to foster a vigilant cybersecurity culture that allows those in charge to identify and promptly respond to any irregularities.

Ultimately, a comprehensive strategy combining risk assessments, technical safeguards such as network segmentation and intrusion prevention, and a well-trained workforce are all essential for navigating the advanced security landscape of PLC systems.


Threat Detection and Prevention

Effectively securing a PLC system hinges on robust threat detection and prevention. Here are a few examples of threat detection and prevention:

1) Implementing intrusion detection and prevention systems helps identify and block unauthorized access or abnormal activities.

2) Real-time monitoring allows swift response to potential threats while preventing system compromise.

3) Regular security audits and vulnerability assessments are essential for proactively identifying weaknesses.

4) OT-based firewalls and access controls are vital for bolstering defenses and limiting unauthorized entry points.

5) Virtual patching wherever standard updates and patches are impractical.

6) Employee training, or retraining, since many misconceptions are firmly held, ensures a vigilant workforce capable of recognizing and reporting potential security risks.

Each of these tactics is part of a greater, holistic approach of combining technological safeguards, regular assessments, and employing a knowledgeable team, which are all part of the imperative threat detection and prevention for PLC systems.


Access Control and Authentication

While it may be challenging in an OT environment, establishing robust access control and authentication mechanisms can be crucial in safeguarding a PLC system. Methods for establishing and implementing the proper authentication and access include:

1) Implementing stringent user authentication protocols ensures only authorized personnel can access and modify critical configurations.

2) Role-based access control further refines permissions, limiting individuals to specific tasks based on their roles.

3) Multi-factor authentication, now prevalent across many digital and technical mediums, adds an extra layer of security by requiring users to verify their identity through multiple means.

Each of these measures fortifies the defense of a PLC system against unauthorized access and potential cyber threats. By implementing these tactics, PLC systems can enjoy enhanced security, safeguarding industrial processes from unauthorized manipulation or disruption.


7 Best Practices to Protect Your PLC Systems from Cybersecurity Threats

In an era where industrial processes rely heavily on Programmable Logic Controllers, safeguarding these systems from cybersecurity threats is paramount. Let’s explore the seven best practices to fortify your PLC systems, ensuring resilience against evolving cyber threats and maintaining the integrity of critical industrial operations.

1. Continuous Monitoring and Analysis

Continuous monitoring and analysis emerge as a cornerstone best practice for shielding PLC systems against cybersecurity threats, giving security or operations managers full visibility of their environment and its vulnerabilities. With greater understanding, managers can implement more effective security measures.

Real-time monitoring tools also detect anomalies or suspicious activities quickly, allowing immediate responses. This proactive approach empowers organizations to identify potential security breaches and mount a rapid and effective mitigation process. Ideally, a built-in IPS (intrusion prevention system) can act to prevent entry entirely.

Moreover, continuous system data analysis provides valuable insights into evolving threat landscapes, facilitating the implementation of robust security measures. Embracing a culture of perpetual vigilance through full visibility, constant monitoring, and analysis reinforces the resilience of PLC systems, safeguarding them against a dynamic and ever-growing spectrum of cyber risks.


2. Effective Password Policies

Implementing effective password policies is another pivotal best practice for safeguarding PLC systems against cybersecurity threats, which admittedly may be difficult since real-life OT culture can rely on shared passwords or even shared factory-default passwords. But with sufficient training and awareness of security issues, the situation can be better than what it generally is.


3. Network Segmentation Strategies

Network segmentation strategies divide the network into isolated segments, each with specific access controls. This means that potential attackers face increased complexity in their lateral movements should they try to attack your PLC system.

With network segmentation, if one segment is breached, the attack’s spread can be contained, preventing unauthorized access to additional PLC components.

This approach limits the attack surface and enhances the system’s overall resilience. Additionally, network segmentation allows for focused security measures on high-priority segments, ensuring that resources are allocated efficiently.

By isolating communication pathways, network segmentation strategies effectively mitigate the risk of lateral movement, unauthorized access, and disruptions, safeguarding the integrity and functionality of your PLC system.


4. Utilizing Intrusion Prevention systems

Utilizing an (IPS) intrusion prevention system is instrumental in fortifying programmable logic controller systems against cybersecurity threats. An IPS continuously monitors network and system activities, identifying anomalous patterns or behaviors that may indicate unauthorized access or malicious activities. By analyzing network traffic and system logs in real time, an IPS acts as a vigilant sentinel, promptly identifying potential threats.

Once an anomaly is detected, the IPS can trigger alerts or take automated actions to mitigate the threat, preventing unauthorized access or tampering with the PLC system. This proactive defense mechanism enhances a PLC system’s resilience by enabling swift responses to otherwise untraceable cyber threats.


5. Secure Remote Access Protocols

Secure remote access protocols fortify PLC systems against cybersecurity threats by ensuring that remote connections are established and maintained with the highest level of security.

Protocols like virtual private network (VPN) and secure shell (SSH) encrypt data during transmission, safeguarding it from interception or tampering. Through the establishment of secure tunnels, these protocols create a protected communication channel between remote users and the PLC system.

Additionally, secure access solutions often incorporate authentication measures, requiring users to prove their identity through credentials or multi-factor authentication before gaining entry. By deploying these protocols, organizations can enable remote monitoring and maintenance without compromising the integrity of the PLC system.


6. Implementing OT Zero Trust Framework

Implementing an Operational Technology (OT) Zero Trust Framework is potentially the most important practice for fortifying your PLC systems against cybersecurity threats. Unlike traditional perimeter-based security models, a zero-trust approach assumes no inherent trust within the network, requiring continuous verification of user identities and devices.

This framework reduces the attack surface by requiring continuous authentication, authorization, and validation of devices and users attempting to access the PLC system. Network micro-segmentation isolates critical components, limiting lateral movement for potential attackers.

Monitoring and anomaly detection in real-time contribute to both rapid threat identification and response. This proactive model ensures that the entire system’s security remains intact even if one aspect is compromised. An OT Zero Trust Framework mitigates risks by fostering a holistic, layered defense strategy while ensuring a dynamic and adaptive security posture.


Protect Your PLC Network With TXOne

In the evolving landscape of industrial control systems, protecting your PLC network with TXOne ensures a fortified defense against cyber threats.

TXOne’s comprehensive cybersecurity solutions prioritize the integrity and reliability of your Programmable Logic Controller network by leveraging advanced threat detection mechanisms, robust access controls, and secure communication protocols.

TXOne creates a resilient shield against unauthorized access, tampering, and potential disruptions, emphasizing proactive measures, such as continuous monitoring and regular security assessments.

Choosing TXOne not only safeguards your PLC network, it also protects the critical industrial processes it manages, giving you superior peace of mind in an era of unprecedented cybercrime.

Protect your PLC network properly by partnering with TXOne today.

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