OT Hardening Implementation
Operational Technology environments are built to keep plants running. Availability, reliability, and safety usually come first, and security is often added later as systems expand and connectivity increases. That reality leaves many OT assets operating with default settings, open services, and inconsistent configurations that were never meant to face today's threat landscape.
Hardening is the practical work of reducing those weaknesses. It is not about adding new tools or redesigning the plant network. It is about tightening what already exists by applying disciplined configuration standards, removing unnecessary exposure, and making systems more consistent across sites and vendors.
Arista Cyber provides OT Hardening Implementation to strengthen the baseline security of controllers, servers, network devices, and supporting infrastructure. The intent is straightforward: reduce the easy paths attackers rely on, without disrupting operations or safety functions.
Hardening is especially valuable in environments with long asset lifecycles, mixed vendor technologies, and legacy systems that cannot be patched frequently. In those settings, configuration discipline often becomes one of the strongest controls available.
LOCK DOWN YOUR OT SYSTEMS—MINIMIZE WEAKNESSES, MAXIMIZE RESILIENCE. HARDENED OT ENVIRONMENTS THAT ATTACKERS CAN’T EASILY EXPLOIT
Why OT Hardening Matters
In many plants, the biggest risk is not a complex, advanced intrusion. It is the combination of small gaps that build up over time: default accounts, unused services left enabled, shared engineering workstations, permissive remote access, or device settings that were never reviewed after commissioning.
These gaps rarely stand out on their own. The issue is how they interact. When configurations vary widely across PLCs, HMIs, RTUs, servers, and network equipment, it becomes difficult to know what "normal" looks like. When configurations vary from device to device, even simple questions take longer to answer. It becomes harder to spot what is unusual, harder to enforce policy consistently, and harder to respond quickly when something goes wrong.
Hardening brings the environment back to a known state. It reduces unnecessary variation and gives teams a baseline they can actually rely on.
Key Advantages
Hardening is about removing the easy wins that attackers look for. Many OT systems were commissioned for uptime and function, and security settings were never revisited afterwards.
1.Reduce attack surface and prevent exploitation.
The work usually comes down to practical changes: disabling what is not needed, tightening permissions, and closing off access paths that serve no operational purpose.
2.Standardise secure configurations across OT assets
Consistent configuration baselines across platforms reduce variability, simplify maintenance, and make it easier to identify abnormal behaviour. Standardisation saves time in the small moments. When configurations are consistent and written down, engineers stop second-guessing settings and spend more time keeping the plant running.
3.Support compliance with industry standards
Hardening also helps with compliance in a practical way. When auditors ask how access, services, and configurations are managed, you have a clear baseline and a record of what was implemented, without scrambling at the last minute.
Reduce weaknesses. Improve resilience. Keep OT environments harder to exploit.
What OT Assets We Harden
Hardening is applied across the OT stack, focusing on improving configuration posture while preserving operational reliability. Our teams concentrate on the real-world devices and systems that run your operations.
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1.PLCs, RTUs, and Control Devices
Tightening access, disabling unnecessary services, reviewing protocol exposure, and aligning configurations to an agreed secure baseline. -
2.HMIs and Engineering Workstations
Improving account controls, standardising software builds, enabling appropriate logging, managing removable media, and ensuring remote use is handled safely. -
3.Servers Supporting OT Operations
Addressing patch posture limitations, securing key services, enforcing role separation, and restricting privileged access. -
4.Network Devices
Securing management access, handling credentials appropriately, disabling unnecessary services, and maintaining consistent configuration standards. -
5.Supporting Components
Hardening remote access gateways, jump hosts, authentication services, and monitoring pathways which enable secure operations.
Hardening methods and choices are always shaped by what is operationally safe for your environment. In OT, “secure” and “stable” must coexist. Our goal is to enhance security without compromising reliability.
Deliverables
Each engagement produces clear outputs your teams can implement, validate, and maintain over time.
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1. Hardening guidelines for OT assets
Practical hardening guidance for PLCs, HMIs, RTUs, servers, and network devices, tailored to your environment and vendor landscape. These guidelines are written in a way that teams can apply consistently across sites. -
2. Compliance-supporting implementation guidance
Recommendations structured to support industry expectations and internal policies. Controls are documented with clarity so teams understand what was changed, why it matters, and how it should be maintained. -
3. Final Hardening Report
A final report summarising:
✔ Systems and asset classes covered
✔ Baseline standards used
✔ Hardening measures applied
✔ Validation steps performed
✔ Resulting configuration posture for key system
This report becomes a practical reference for governance, audits, and future maintenance cycles.
Our Approach
Hardening only works when it is handled like engineering work. Changes have to be controlled, validated, and introduced safely, because availability and safety still come first.
1) Assess current OT configurations
We begin by reviewing how the organization’s OT assets are currently configured today. This typically includes identifying:
✔ Default or weak account practices
✔ Unnecessary services and ports
✔ Inconsistent settings across similar devices
✔ High-risk configurations that add exposure without operational value
✔ Areas where changes must be handled carefully due to safety or uptime constraints
The outcome is a clearer picture of what is consistent, what has drifted over time, and where the environment is most exposed.
2) Apply recognised hardening practices and standards
Next, we apply hardening measures that make sense for industrial systems and can be maintained by your teams. The focus is on practical improvements that can realistically be maintained, rather than theoretical controls that teams will bypass.
Hardening measures may include secure configuration baselines, role-based access improvements, service reduction, configuration standardisation, and tightening of administrative pathways.
3) Validate changes before deployment
Before changes touch production systems, we validate them in a non-production environment wherever possible. This step is about avoiding surprises. Testing helps confirm that the changes behave as expected and do not interfere with process operations.
If a non-production environment is not available, rollout is planned with operational stakeholders, introduced in a controlled way, and supported with clear rollback planning.
4) Document, hand over, and support adoption
Hardening is not "done" unless it can be maintained. We provide documentation and implementation notes that make it easier to keep the baseline intact and prevent gradual configuration drift.
Proven Standards & Expertise
Industrial cybersecurity is built on strong governance. Our methodology fits cleanly into the standards and practices your teams already follow:
- ✔ IEC 62443: Defines secure zones, conduits, and responsibilities for managing industrial assets
- ✔ NIST CSF (ID.AM): Ensures critical equipment is identified, documented, and protected
The outcome is greater confidence in your operations and an easier conversation with regulators when the time comes.
Highlights
- ✔ Minimise exploitable weaknesses
- ✔ Standardised OT security configurations
- ✔ Improved regulatory compliance
Where Hardening Adds the Most Value
Hardening delivers the strongest return in environments where:
- 1. Legacy systems cannot be easily patched or upgraded
- 2. Multiple vendors and device types make consistency difficult
- 3. Remote access and support connections are common
- 4. OT and IT boundaries are blurred
- 5. Audit or regulatory scrutiny is increasing
Ready to Strengthen Your OT Baseline?
Hardening is one of the most practical ways to reduce risk in OT because it improves the security posture of what you already operate. It also makes the environment easier to manage, monitor, and defend over time.
If you want to reduce exploitable weaknesses and bring consistency to OT configurations without disrupting operations, Arista Cyber can help you implement hardening measures that are standards-aligned, operationally safe, and maintainable.
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