Top 15 Industrial Cybersecurity Mistakes – and How to Avoid Them

Industrial environments are unique: safety and availability are non-negotiable, equipment lifecycles are measured in decades, and IT security approaches often break processes they weren’t designed to protect. Attackers know this and increasingly weaponize OT weak points to cause physical impact, financial loss, and regulatory pain. This post breaks down the 15 most common industrial cybersecurity mistakes I see in the field, explains why they matter in plain language, and gives concrete, prioritized actions you can implement now – aligned to NIST, ISA/IEC 62443, and current federal guidance.

Quick reality check (brief background)

• OT has rapidly converged with IT: remote access, cloud analytics, and IIoT sensors now sit beside PLCs and DCSes. This integration improves efficiency – and attack surface. Standards and guidance (NIST SP 800-82 Rev.3, IEC/ISA 62443, and CISA advisories) now emphasize OT-specific controls: asset visibility, zones & conduits, safe patching practices, and OT incident response. Use them as your baseline. Real incidents continue to rise and evolve – targeted malware families and supply-chain/third-party vectors put operations at risk. Recent reporting shows notable OT incidents every quarter.

1) No reliable asset inventory (or it’s out of date)

What it looks like: Teams rely on tribal knowledge, spreadsheets, or partial discovery of devices. Unknown devices, unmanaged PLCs, and forgotten HMIs live on the network.
Why risky: You can’t protect what you can’t see. Untracked devices often run unpatched firmware or default credentials – prime targets.
How to avoid it:

• Deploy passive and active OT asset discovery tools and reconcile with CMDBs.
• Maintain firmware, software versions, and ownership metadata.
• Automate discovery and set a quarterly reconciliation cadence. (Short term: passive sensors; long term: integrate into configuration/CMDB.)

2) Poor network segmentation (flat OT/IT networks)

What it looks like: OT and IT reside on the same flat network or segmentation is implemented only at firewalls without zone/conduit design.
Why risky: Lateral movement becomes trivial; an IT breach can rapidly affect plant safety and availability.

How to avoid it:

• Design zones & conduits per IEC/ISA 62443. Limit east-west traffic; enforce least privilege.
• Microsegment critical systems (HMIs, engineering workstations, PLCs).
• Use industrial protocol proxies/gateways rather than open routing for cross-zone traffic.

3) Default or weak credentials still in use

What it looks like: HMIs, controllers, or vendor tools using default accounts or shared passwords.
Why risky: Credential reuse and defaults are trivial for opportunistic attackers and are still a factor in many ICS incidents.

How to avoid it:

• Enforce unique, strong credentials and MFA where feasible on engineering and remote accounts.
• Rotate service and vendor accounts regularly; record them in vaults.

4) Uncontrolled remote access (and unmanaged third-party connectivity)

What it looks like: VPNs or remote tools installed ad-hoc, vendor access given without monitoring, or remote desktops open to business networks.
Why risky: Remote access is a common initial access vector; insecure third-party access has led to several production outages.
How to avoid it:

• Replace ad-hoc VPNs with brokered, logged remote access (jump hosts, bastion hosts, Zero Trust Network Access).
• Enforce time-boxed vendor sessions, session recording, and least-privilege vendor accounts.
• Monitor and alert on unusual remote sessions.

5) Weak patching strategy (or none at all)

What it looks like: Devices running obsolete firmware, unpatched vulnerabilities ignored due to fear of downtime.
Why risky: Nation-state-grade toolkits and commodity exploit kits routinely weaponize known ICS vulnerabilities; CISA publishes commonly exploited vulnerabilities yearly.
How to avoid it:

• Establish a risk-based patch program: test patches in a staging replicant before production.
• Prioritize critical vulnerabilities impacting safety controllers and communication stacks.
• Use compensating controls (network isolation, virtual patching) where immediate patching is impractical.

6) Treating OT cybersecurity like IT (copy-paste IT controls)

What it looks like: Applying business IT endpoint tooling or automatic patching that interferes with real-time control.
Why risky: OT devices have real-time constraints – some IT controls can break safety functions or degrade performance.
How to avoid it:

• Use OT-aware tools and vendors that support safe modes and maintenance windows.
• Align change windows with production schedules and safety engineers.
• Map each control to safety/availability impact before deployment.

7) No OT-specific incident response plan (or it’s untested)

What it looks like: IR playbooks are IT-centric, missing procedures for evacuation, safe shutdown, or forensic capture of PLCs.
Why risky: Mishandled response can create greater safety hazards than the attack itself.
How to avoid it:

• Create OT IR playbooks with process engineers, operators, and field technicians.
• Run tabletop and full-scale drills at least annually with third parties/venders.
• Define roles (OT lead, safety officer, comms lead) and escalation paths.

8) Insufficient logging and monitoring (no OT telemetry)

What it looks like: Logs either not captured or routed only to local devices; no correlation with enterprise SIEM or OT-aware SOC.
Why risky: Attacks often show subtle signs – drift in setpoints, unauthorized engineering tool use – which are missed without telemetry and baselining.
How to avoid it:

• Implement OT-aware monitoring (protocol decoding, anomaly detection for PLC/SCADA behavior).
• Integrate OT logs with SOC workflows and playbooks.
• Create baselines for normal process values and alert on deviations.

9) Insecure industrial protocols and exposed services

What it looks like: OPC Classic, Modbus, or older protocols exposed outside proper boundaries or proxied without authentication.
Why risky: Many legacy protocols lack authentication and are trivially manipulated; exposure invites immediate compromise.
How to avoid it:

• Use protocol gateways, OPC UA with security profiles, and dedicated protocol inspectors.
• Block or proxy legacy protocols at zone boundaries.

10) Over-trusting vendors / weak procurement security clauses

What it looks like: Vendors deliver equipment with insecure defaults, or SLAs without vulnerability disclosure and patch commitments.
Why risky: Product insecurity and supply-chain weaknesses are systemic; vendors must be contractually obligated to help remediate.
How to avoid it:

• Add security requirements to RFPs (secure development lifecycle, vulnerability disclosure, patch timelines).
• Require SBOMs (software bill of materials) and memory safety roadmaps where applicable.
• Test and harden vendor gear in a lab before production deployment.

11) No configuration management (drift and undocumented changes)

What it looks like: Engineers make manual changes on-the-fly; no versioned backups of PLC logic or HMI screens.
Why risky: Unauthorized or undocumented changes cause downtime, complicate incident investigations, and can introduce vulnerabilities.
How to avoid it:

• Implement version control for PLC logic and HMI configurations.
• Use change approval workflows and track changes to a CMDB.
• Backup configurations regularly and test restores.

12) Poor business case for OT security (underfunding & misplaced priorities)

What it looks like: OT security projects stalled; leadership thinks ‘it won’t happen to us’.
Why risky: Lack of funding prevents basic hygiene, increasing probability and impact of incidents. Strengthening OT reduces downtime and safety risk – a measurable ROI.
How to avoid it:

• Build quantitative risk cases (cost of downtime, regulatory fines, safety liability).
• Start with high ROI projects: asset inventory, segmentation, and remote access controls.

13) Ignoring human factors (poor operator training & permissions)

What it looks like: Shared admin accounts, inadequate training for anomaly detection, or operators performing insecure workarounds.
Why risky: Human error (misconfiguration, credential misuse) remains a leading contributor to incidents.
How to avoid it:

• Train operators on cyber hygiene and spotting abnormal behavior.
• Enforce least privilege and remove shared admin accounts.
• Capture runbooks and safe fallback steps for common tasks.

14) Skipping safety/cyber crosswalks (no coordinated safety & cyber engineering)

What it looks like: Cyber measures implemented without assessing impact on process safety or HAZOP outcomes.
Why risky: Cyber changes can inadvertently interfere with protective functions; safety and cyber must be engineered together.

• Include safety engineers in cyber change approvals and incident exercises.
• Conduct cyber-aware HAZOPs and document cyber controls that intersect with safety instrumented systems (SIS).

15) Not testing defenses (no red-team, no OT pen tests)

What it looks like: Confidence that controls work without adversarial testing; assessments limited to IT controls.
Why risky: Only adversarial testing reveals realistic attack paths, supply-chain assumptions, and human gaps. Real incidents show attackers adapt quickly.
How to avoid it:

• Run OT-capable red teams and scoped penetration tests with safety controls and rollback plans.
• Use honeypots in labs to study attacker TTPs in a controlled environment.

Turning fixes into a program – a 90-day prioritized playbook

Week 1–4 (stabilize): Asset inventory, identify critical assets, lock down default credentials, and implement basic remote access controls.
Month 2 (harden): Apply segmentation (zones & conduits), deploy OT logging, and set up vendor session recording.
Month 3 (mature): Formalize patching risk model, run IR tabletop, add contractual vendor security requirements, and schedule red-team/pen tests.
This phased approach gives fast risk reduction while building the capability to sustain improvements over time.

Practical toolkit & checklist

• Passive asset discovery sensor deployed.
• Mapped zones & conduits diagram with access policy.
• Unique credentials + vault for all privileged accounts.
• Brokered remote access with session recording.
• OT-aware monitoring feeding SOC alerts.
• Change control + PLC logic backups.
• Annual OT IR tabletop and at least one live exercise in three years.
• Vendor security clauses: SBOM, patch SLA, vulnerability disclosure.
• Red-team/pen test every 12 months.

Conclusion

Industrial cybersecurity is no longer a secondary priority-it is a core operational requirement. As threats evolve and industrial environments become increasingly interconnected, organizations must shift from reactive security to a proactive, standards-driven approach. The most damaging OT incidents rarely occur because of a single catastrophic failure; instead, they emerge from a combination of unnoticed gaps, outdated practices, and uncoordinated processes across engineering, operations, and IT.

By recognizing and addressing the 15 critical mistakes outlined in this guide, asset owners can significantly strengthen their cyber maturity, reduce operational risk, and improve overall resilience. The path forward is not about deploying the most complex tools, but about getting the fundamentals right: visibility, segmentation, secure remote access, disciplined change management, skilled people, and a well-tested incident response plan.

Cybersecurity in OT is a continuous journey. Each improvement-however small-directly contributes to plant safety, uptime, and regulatory compliance. When organizations commit to long-term governance, cross-functional collaboration, and continuous testing, they build an operational environment that can withstand both modern cyber threats and the unexpected challenges of digital transformation.

Strengthening OT security is not just about protection; it is about enabling safer, smarter, more reliable industrial operations for the future. Let your cybersecurity program become a strategic advantage-not a vulnerability.