implementing-purdue-model-network-segmentation

name	implementing-purdue-model-network-segmentation
description	Implement network segmentation based on the Purdue Enterprise Reference Architecture (PERA) model to separate industrial control system networks into hierarchical security zones from Level 0 physical process through Level 5 enterprise, enforcing strict traffic control between OT and IT domains. . Use when working with implementing purdue model network segmentation.
domain	cybersecurity
tags	["ot-security","ics","purdue-model","network-segmentation","iec62443","defense-in-depth","dmz","scada"]
subdomain	ot-ics-security
version	1.0
author	oyi77
license	Apache-2.0
nist_csf	["PR.IR-01","DE.CM-01","ID.AM-05","GV.OC-02"]

Implementing Purdue Model Network Segmentation

Overview

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

When to Use

Trigger phrases:

• "implementing purdue model network segmentation"

• "Implement network segmentation based on the Purdue Enterprise Reference Architec"

• When designing or retrofitting network architecture for an ICS/SCADA environment

• When implementing IEC 62443 zone and conduit requirements in a brownfield plant

• When creating the IT/OT DMZ (Level 3.5) to control data flow between enterprise and control networks

• When remediating audit findings about flat OT networks or direct IT-to-OT connectivity

• When segmenting a converged IT/OT network after an acquisition or merger

Do not use for micro-segmentation within a single Purdue level (see implementing-zone-conduit-model-for-ics), for cloud-native environments without traditional ICS networks, or for network segmentation in purely IT environments.

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 OT asset inventory with Purdue level classification for each device
• Network architecture diagram showing current topology, VLANs, and firewall placements
• Industrial firewalls capable of deep packet inspection for OT protocols (Palo Alto, Fortinet, Cisco)
• Understanding of required data flows between Purdue levels (historian replication, remote access, patch distribution)
• Change management approval from plant operations for network modifications

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()}