implementing-network-segmentation-for-ot

name	implementing-network-segmentation-for-ot
description	Use when this skill covers implementing network segmentation in Operational Technology environments using VLANs, industrial firewalls, data diodes, and software-defined networking. It addresses the Purdue Model-based segmentation strategy, migration from flat networks to segmented architectures without disrupting operations, configuring OT-aware firewalls with industrial protocol deep packet inspection, and validating segmentation effectiveness through traffic analysis.
domain	cybersecurity
tags	["ot-security","ics","scada","industrial-control","iec62443","network-segmentation","vlan"]
subdomain	ot-ics-security
version	1.0.0
author	oyi77
license	Apache-2.0
nist_csf	["PR.IR-01","DE.CM-01","ID.AM-05","GV.OC-02"]

Implementing Network Segmentation For Ot

Overview

Cybersecurity skill for implementing network segmentation for ot. Follows industry best practices and security standards.

When to Use

Trigger phrases:

• "implementing network segmentation for ot"

• "This skill covers implementing network segmentation in Operational Technology en"

• When an OT security assessment reveals a flat network with no segmentation between Purdue levels

• When implementing IEC 62443 zone/conduit architecture after completing risk assessment (IEC 62443-3-2)

• When separating IT and OT networks as part of an IT/OT convergence security initiative

• When deploying a DMZ between corporate IT and OT to protect industrial systems from IT-originating threats

• When segmenting safety instrumented systems (SIS) from basic process control systems (BPCS)

Do not use for IT-only microsegmentation without OT components (see implementing-zero-trust-in-cloud), or for initial zone design without prior traffic analysis (see performing-ot-network-security-assessment first).

When NOT to Use

• When you lack proper authorization for testing
• For production systems without change management
• When the task requires legal or compliance expertise beyond technical scope

Prerequisites

• Complete traffic baseline from passive monitoring (minimum 2-4 weeks of capture data)
• Asset inventory with Purdue level classifications for all OT devices
• Industrial-grade network switches with VLAN support and port security
• OT-aware firewalls (Cisco ISA-3000, Fortinet FortiGate Rugged, Palo Alto with OT Security)
• Maintenance window schedule for network changes
• Rollback plan approved by operations management

Workflow

# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def () -> :
     {k: re.findall(v, text)  k, v  IOC_PATTERNS.items()}