Enhancing HMI Security: How To Protect ICS Environments From Cyber Threats

GUIs and remote access can provide an entry point for bad actors.


HMIs (Human Machine Interfaces) can be broadly defined as just about anything that allows humans to interface with their machines, and so are found throughout the technical world. In OT environments, operators use various HMIs to interact with industrial control systems in order to direct and monitor the operational systems. And wherever humans and machines intersect, security problems can ensue.

Protecting HMI in cybersecurity plans, particularly in OT/ICS environments, can be a challenge, as HMIs offer a variety of vulnerabilities that threat actors can exploit to achieve any number of goals, from extortion to sabotage.

Consider the sort of OT environments HMIs are found in, including water and power utilities, manufacturing facilities, chemical production, oil and gas infrastructure, smart buildings, hospitals, and more. The HMIs in these environments offer bad actors a range of attack vectors through which they can enter and begin to wreak havoc, either financial, physical, or both.

What’s the relationship between HMI and SCADA?

SCADA (supervisory control and data acquisition) systems are used to acquire and analyze data and control industrial systems. Because of the role SCADA plays in these settings — generally overseeing the control of hugely complex, expensive, and dangerous-if-misused industrial equipment, processes, and facilities — they are extremely attractive to threat actors.

Unfortunately, the HMIs that operators use to interface with these systems may contain a number of vulnerabilities that are among the most highly exploitable and frequently breached vectors for attacks against SCADA systems.

Once an attacker gains access, they can seize from operators the ability to control the system. They can cause machinery to malfunction and suffer irreparable damage; they can taint products, steal information, and extort ransom. Even beyond ransom demands, the cost of production stoppages, lost sales, equipment replacement, and reputational damage can swallow some companies and create shortages in the market. Attacks can also cause equipment to perform in ways that threaten human life and safety.

Three types of HMIs in ICS that are vulnerable to attack

HMI security has to account for a range of “vulnerability options” available for exploitation by bad actors, such as keyboards, touch screens, and tablets, as well as more sophisticated interface points. Among the more frequently attacked are the Graphical User Interface and mobile and remote access.

Graphical User Interface

Attackers can use the Graphical User Interface or GUI to gain complete access to the system and manipulate it at will. They can often gain access by exploiting misconfigured access controls or bugs and other vulnerabilities that exist in a lot of software, including GUI software. If the system is web- or network-connected, their work is easier, especially if introducing malware is a goal. Once in, they can also move laterally, exploring or compromising interconnected systems and widening the attack.

Mobile and remote access

Even before COVID-19, mobile and remote access techniques were already being incorporated into managing a growing number of OT networks. When the pandemic hit hard, remote access often became a necessity. As the crisis faded, however, mobile and remote access became even more entrenched.

Remote access points are especially vulnerable. For one, remote access software can contain its own security vulnerabilities, like unpatched flaws and bugs or misconfigurations. Attackers may find openings in VPNs (virtual private networks) or RDP (remote desktop protocol) and use these holes to slip past security measures and carry out their mission.

Access controls

Attackers can compromise access control mechanisms to acquire the same permissions and privileges as authorized users, and once they gain access, they can do pretty much anything they want regarding system operations and data access. Access can be gained in many of the usual ways, such as an outdated VPN or stolen or purchased credentials. (Stolen or other credentials are readily available through online markets.)

The initial attack may just be a toe in the network while reconnaissance for holes in the access control system is conducted. Weak passwords, unnecessary access rights, and the usual misconfigurations and software vulnerabilities are all an attacker needs. As further walls are breached, attackers can then escalate their level of privilege to do whatever a legitimate user can do.

Understanding attack techniques in ICS HMI cybersecurity

Code injection

When attackers insert or inject malicious code into a software program or system, that’s code injection, and it can give the attacker access to core system functions. The resulting mayhem can include manipulation of control software, leading to shutdowns, equipment damage, and dangerous, even life-threatening situations if system changes result in hazardous chemical releases, changed formulas, explosions, or the misbehavior of large, heavy machinery. Code injections can corrupt, delete, or steal data and may result in compliance failure and fines in certain situations.

Malware virus infection

Malware can enter a network through various access points in addition to HMIs, even ones no one would ever expect, such as manufacturer-provided software updates or factory-fresh physical assets added to the production environment. A technician connecting a laptop or an employee plugging in a flash drive without knowing it’s infected will work just as well. As the walls between IT and OT thin, that attack surface widens as well. Once in the network, the attacker can escalate privileges, look around a bit, and see what’s worth doing or stealing. When enough has been learned, the attacker executes the malicious code, which can include ransomware or spyware. As in other attacks, operations can be interfered with, sometimes dangerously so.

Data tampering

Data tampering simply means that data is altered without authorization, including data used to operate, control, and monitor industrial systems. Attackers gain access through vulnerabilities in the system software or HMI devices or through passageways between IT and OT. Once in, they can explore the system to give themselves even greater access to more sensitive areas, where they can steal valuable and confidential system data, interrupt operations, compromise equipment, and damage the company’s business interests and competitive advantage.

Memory corruption

Memory corruption can happen in any computer network and may not represent anything nefarious. Yet memory corruption has also been used as an attack technique that can be deployed against OT networks and is thus potentially extremely damaging since data controls machinery, processes, formulas, and other essential functions. Attackers find software vulnerabilities in HMI or other access points through which the memory of an application or system can be reached and corrupted. This can lead to crashes, data leakage, denial of services (DoS), and even attacker takeovers of ICS and SCADA systems.

Spear phishing

Spear phishing attacks are generally launched against IT networks, which can then be used to open a corridor to the OT network. Spear phishing is basically a more targeted version of phishing attacks, in which an attacker will impersonate a legitimate, trusted source via email or web page, for example. In 2014, attackers targeted a German steel mill with an email suspected of carrying malicious code. They then used access to the business network to get to the SCADA/ICS network, where they modified the PLCs (programmable logic controllers) and took over the furnace’s operations. The physical damage they inflicted forced the plant to shut down.

DoS and DDoS attacks

Denial of Service (DoS) and Distributed Denial of Service (DDoS) work by overwhelming HMI points with excessive traffic or requests so they are unable to handle authorized control and monitoring functions. In 2016, some particularly vicious malware dubbed Industroyer (also Crashoveride) was deployed in an attack against Ukraine’s power grid and blacked out a substantial section of Kyiv. Industroyer was developed specifically to attack ICS and SCADA systems. The multipronged attack began by exploiting vulnerabilities in digital substation relays. A timer regulating the attack executed a distributed denial-of-service (DDoS) attack on every protection relay on the network that used any of four specific communication protocols. Simultaneously, it deleted all MicroSCADA-related files from the workstations’ hard drives. As the relays stopped functioning, lights went out across the city.

Exploiting remote access

The growing use of remote access to HMI systems during and after COVID-19 has provided threat actors with a wealth of newly available attack vectors. Less-than-airtight remote access security protocols make them very enticing for ICS-specific malware. HAVEX malware, for example, uses a remote access trojan (RAT) downloaded from OT vendor websites. The RAT can then scan for devices on the ports commonly used OT assets, collect information, and send it back to the attacker’s command and control server. A long-term attack used just such a method to gain remote access to energy networks in the U.S. and internationally, during which data thieves collected and “exfiltrated” (stole) enterprise and ICS-related data.

Credential theft

Obtaining unauthorized credentials is not all that difficult these days, with a robust online marketplace making it easier than ever. Phishing and spear phishing, malware, weak passwords, and vulnerabilities or misconfigurations that grant access to places where unencrypted credentials are all sources. With credentials in hand, attackers can move past security, including MFA (multifactor authentication), conduct reconnaissance, and give themselves whatever level of privilege they need to complete whatever their mission is. Or they simply persist and observe, learning all they can before finally acting against the ICS or SCADA system.

Zero-day attacks

Zero-day attacks got their name because they’re generally carried out against a previously existing yet unknown vulnerability; the vendor has zero days to fix it because the attack is already underway. Vulnerabilities that are completely unknown to either the software developer or the cybersecurity community exist throughout the software world, including in OT networks and their HMIs. Unsuspected and thus unpatched, they give fast-moving threat actors the opportunity to carry out a zero-day attack without resistance. The 2010 Stuxnet attack against Iran’s nuclear program used zero-day vulnerabilities in Windows to access the network and spread, eventually destroying the centrifuges. One thousand machines sustained physical damage.

Best practices for enhancing HMI security

Network segmentation for isolation

Network segmentation should be a core defense in securing industrial networks. Segmentation creates an environment that’s naturally resistant to intruders. Many of the attack techniques described above give attackers the ability to move laterally through the network. Segmenting the network prevents this lateral movement, limiting the attack radius and potential for damage. As OT networks become more connected to the world and the line between IT and OT continues to blur, network segmentation can segregate HMI systems from other parts of the network and the outside world. It can also segment defined zones within the OT network from each other so attacks can be contained.

Software and firmware updates

Software and firmware updates are recommended in all cybersecurity situations, but installing patches and updates in OT networks is easier said than done. OT networks prioritize continuous operations. There are compatibility issues, unpatchable legacy systems, and other roadblocks. The solution is virtual patching. Virtual patching is achieved by identifying all vulnerabilities within an OT network and applying a security mechanism such as a physical IPS (intrusion prevention system) or firewall. Rules are created, traffic is inspected and filtered, and attacks can be blocked and investigated.

Employee training on cybersecurity awareness

The more employees know about network operations, vulnerabilities, and cyberattack methods, the more they can do to help protect the network. Since few organizations have the internal staff to provide the necessary training, third-party training partners can be a viable solution. In any event, all employees should be trained in a company’s written policies, the general threat landscape, security best practices, how to handle physical assets like flash drives or laptops, how to recognize an attack, and what the company’s response protocol is. Specific training should be provided for employees who work remotely.

The evolving HMI security threat landscape

Concrete predictions about future threats and responses are hard to make, but the HMI security threat landscape will most likely evolve much the same way the entire security landscape will, with one major addition.

Air-gapped environments are going away

For a long time, many OT networks were air-gapped off from the world, physically and digitally isolated from the risks of contamination. Data and malware transfer alike required physical media, but inconvenience was safety. As OT networks continue to merge with the connected world, that kind of protection is going away. Remote work is becoming more prevalent, and the very connected IoT (Internet of Things) is now all over the automated factory floor. If wireless access points are left hanging from equipment, no one gives it a thought, except threat actors looking for a way in. (This is where basic employee training might help.)

Threat actors are innovators

Threat actors are becoming increasingly sophisticated. They devote much more time and thought to innovative ways to penetrate HMI and other OT network points than the people who operate them. AI and machine learning techniques are further empowering bad actors.

The statistics bear this out, especially as IT and OT networks continue to converge. In a study on 2023 OT/ICS cybersecurity activities, 76% of organizations were moving toward converged networks, and 97% reported IT security incidents also affected OT environments. Nearly half (47%) of businesses reported OT/ICS ransomware attacks, and 76% had significant concerns about state-sponsored actors.

On the positive side, however, pressure from regulators, insurance companies, and boards of directors is pushing organizations to think and act on cybersecurity for HMI points and throughout the network far more aggressively than many currently do. According to the study, 68% of organizations were increasing their budgets, 38% had dedicated OT security teams, and 77% had achieved a level-3 maturity in OT/ICS security.

Complete OT security

Cybersecurity in industrial environments presents challenges far different than those in IT networks. TXOne specializes in OT cybersecurity, with OT-native solutions designed for the equipment, environment, and day-to-day realities of industrial settings.

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