The Difference Between IT and OT Cybersecurity: Explained

In environments where keeping the lights on is a literal promise, network security isn’t just about protecting emails or customer databases. Fundamental safety, uptime, and sometimes even human lives are at stake. As digitalization has crept into operational technology (OT) environments—industrial control systems (ICS), supervisory control and data acquisition (SCADA), and other building- and infrastructure-critical tools—the line between IT and OT cybersecurity becomes messy and, for many, a source of confusion and organizational friction.

Let’s break down how IT and OT security differ, why those distinctions matter, and what this means for network architects, CISOs, and the operators living at the intersection of both worlds.

Historic Roots: How Did We Get Here?

Classic IT: Origin in Business Computing

IT, or Information Technology, cut its teeth on mainframes, office networks, email servers, and enterprise applications. Security priorities were shaped by confidentiality and data integrity. IT cared most about who had access to what, protecting business data (financials, IP, PII), and maintaining system reliability, albeit often with downtime windows and patch cycles planned during off-hours.

Typical IT stack:

• TCP/IP-based communication (Ethernet, Wi-Fi)

• Client/server architectures

• Authentication (LDAP, Kerberos, Active Directory)

• Patchable OSes (Windows, Linux, etc.)

• Firewalls, VPNs, IDS/IPS systems

Classic OT: Origins in Isolation and Determinism

OT, or Operational Technology, refers to the hardware and software controlling the physical world: power stations, water treatment plants, manufacturing lines. Traditional OT systems evolved for reliability and real-time determinism, not for interaction with the outside world. They ran proprietary protocols over serial lines, lived on air-gapped networks, and focused on keeping operations up, sometimes with vendor ‘black boxes’ untouched for decades.

Typical OT stack:

• Fieldbus, Modbus, Profibus, proprietary serial protocols

• PLC (Programmable Logic Controllers), RTUs, DCS (Distributed Control Systems)

• Deterministic responses, millisecond timing, minimal downtime

• Default/no authentication, static configuration

• Rare patching—if ever (sometimes, “run to fail”)

The Great Collision

The push for viewability, optimization, and efficiency—via dashboards, analytics, cloud integrations—has driven a convergence between IT and OT. It’s impractical (and risky) to expect operational islands, and as a result, OT security has been forced to confront the harsh realities of the open Internet.

Key Differences Between IT and OT Security

1. Security Priorities: CIA vs. AIC

IT and OT share the same letters but not the priorities.

In OT, Availability-Integrity-Confidentiality (AIC) is the dominant model—downtime means lost production, not “just” annoyed employees.

2. Asset Lifecycle and Patch Management

• IT: 3-5 year lifecycle typical for endpoints and servers. Patching is continuous, sometimes automated (think Microsoft Patch Tuesday).

• OT: 10, 15, or even 20-year asset life is not uncommon. Many devices can’t be rebooted without scheduling plant downtime, and some aren’t patchable in practice. “If it ain’t broke, don’t touch it.”

3. Protocols and Standards

IT is built on the TCP/IP stack, with universal protocols (HTTP, DNS, SMB, etc.). OT deals with a zoo of vendor-specific and legacy protocols—many of which have zero security baked in (e.g., Modbus, DNP3).

Modbus, developed in 1979 for industrial control, has no authentication or encryption; anyone with network access can send commands to devices.

Interfacing these often demands specialized equipment (protocol converters, data diodes), and attempting to overlay classic IT controls can break fragile OT systems.

4. Threat Landscape and Risk Tolerance

IT is about protecting data, managing insider threats, and stopping phishing/ransomware. OT attacks can cause physical destruction or safety incidents. Well-known examples include:

• Stuxnet (2010): First ‘cyber-weapon’ targeting PLCs to sabotage Iran’s nuclear centrifuges.

• Ukraine power grid (2015, 2016): Attackers disabled substations, causing massive blackouts via manipulated OT systems.

• Colonial Pipeline (2021): Ransomware disrupted fuel supplies, impacting millions.

OT operators live in fear of unintended consequences. Applying a new security control that blue-screens a historian server or glitches a PLC isn’t a minor error—it can halt operations, or worse.

5. Organizational Silos

Historically, IT and OT teams operated in parallel, rarely collaborating. OT was the purview of engineers, not system admins; networking meant serial cabling and proprietary switches. Security mindsets, language, and risk calculations differ, complicating efforts for unified defense.

Architectural Challenges: IT/OT Integration

Network Segmentation

The best practice: segregate IT and OT networks using firewalls, demilitarized zones (DMZs), and tightly controlled jump hosts.

In 1999, the Purdue Enterprise Reference Architecture emerged as a de facto model for industrial networks, defining six layers from corporate IT (Level 5) down to field devices (Level 0).

Purdue Model Layers:

• Level 5: Enterprise (ERP, email, Internet)

• Level 4: Business (site-level IT)

• Level 3: Operations (site-wide control, SCADA)

• Level 2: Control (line/area control)

• Level 1: Basic control (PLCs, sensors, actuators)

• Level 0: Physical processes (machinery, valves, relays)

Segmentation is crucial, but reality intervenes: organizations often find flat networks, unauthorized cross-connections, and vendors demanding remote access for support.

Remote Access and Third-Party Risk

Remote support is a recurring pain point: field engineers need access, often via insecure methods (default VPNs, TeamViewer). Controlling and monitoring these access paths—without breaking critical support—is an ongoing struggle.

Visibility and Asset Inventory

IT networks are discoverable with tools (Nmap, SNMP, Netflow). OT devices aren’t always as legible. Many have no logs, no host-based agents, and are rendered invisible to traditional scanners (which can cause outages). Passive monitoring, network taps, and traffic analysis are often necessary.

Strategies for Bridging the Gap

1. Collaboration, Not Turf Wars

Deep integration between IT security and OT engineering is still rare. Successful convergence requires building basic cross-discipline literacy on both sides. Get OT engineers involved in risk assessments. Train security teams in process control basics. Institutionalize joint incident response exercises. Don’t make security “something done to OT”—it must be with and by them.

2. Asset Criticality Assessments

All devices are not equal. Map out which assets are safety-critical, which can be rebooted, which have direct physical impact. Tailor security controls accordingly. The same control set for enterprise printers and PLCs is, frankly, reckless.

3. Defense-in-Depth Adapted for OT

Layered defense—network segmentation, protocol whitelisting, anomaly detection, application allow-listing—remains valid, but controls must be calibrated to avoid “collateral damage.” Hyperactive NIDS, poorly planned network scans, or overbearing endpoint protection can easily crash legacy OT gear.

4. Secure Connectivity: Practical Steps

• Use jump hosts and unidirectional gateways for remote access where possible.

• Deploy network access control (NAC), but validate device compatibility first.

• Invest in passive network detection for OT environments—if you don’t know what’s talking, you can’t defend it.

• Carefully manage credentials and access: remove factory defaults, segment by role, audit regularly.

5. Plan for “Forever” Devices

Budget and plan for the fact that some OT endpoints are unpatchable. This may require additional isolation layers, virtual patching at the network level, or highly-customized mitigations. Threat modeling must reflect real-world constraints, not theoretical best practices.

Conclusions: Understanding the Boundaries—and Where They Blur

Cybersecurity for IT and OT has fundamentally different priorities, rooted in their technological evolution and in the physical risks at play. IT can frequently “patch and reboot.” OT must “protect and operate” in environments deliberately built for availability before digital security was even a consideration. As organizations push for more data, more integration, and more automation, the borders between IT and OT will continue to dissolve—but those foundational differences don’t just disappear.

For CISOs, architects, and network engineers, the path forward isn’t to treat OT like another branch office. Respect the legacy, build bridges between disciplines, and deploy controls ruthlessly tailored—and always with an eye toward the realities on the operations floor.

Further Reading

• NIST SP 800-82: Guide to Industrial Control Systems (ICS) Security

• ISA/IEC 62443: Industrial communication networks – Network and system security

• MITRE ATT&CK for ICS: Understanding adversary behavior in industrial environments

• The History of the Purdue Model: ISA InTech: The Purdue Model and Its Impact on ICS Security