# Detecting Dnp3 Protocol Anomalies

> Use when detect anomalies in DNP3 (Distributed Network Protocol 3) communications used in SCADA systems by monitoring for unauthorized control commands, firmware update attempts, protocol violations, and deviations from baseline traffic patterns using deep packet inspection and machine learning approaches. . Use when working with detecting dnp3 protocol anomalies.

- Skill: `oyi77/detecting-dnp3-protocol-anomalies` (Agent Skill)
- Install (CLI): `npx skillmds add oyi77/detecting-dnp3-protocol-anomalies`
- Raw SKILL.md: https://api.skillmd.com/api/skills/oyi77/detecting-dnp3-protocol-anomalies/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: Apache-2.0
- Author: oyi77 (https://skillmd.com/u/oyi77)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/oyi77/detecting-dnp3-protocol-anomalies

---


# Detecting Dnp3 Protocol Anomalies

## Overview

Cybersecurity skill for detecting dnp3 protocol anomalies. Follows industry best practices and security standards.

## When to Use
**Trigger phrases:**
- "detecting dnp3 protocol anomalies"
- "Detect anomalies in DNP3 (Distributed Network Protocol 3) communications used in"


- When monitoring SCADA systems in the energy sector where DNP3 is the primary protocol
- When building detection rules for DNP3-based attacks against RTUs and substations
- When investigating suspected unauthorized control commands sent via DNP3
- When deploying IDS with DNP3 deep packet inspection at utility substations
- When responding to alerts from OT monitoring platforms about DNP3 traffic anomalies

**Do not use** for non-DNP3 protocol monitoring (see detecting-modbus-command-injection-attacks for Modbus), for DNP3 Secure Authentication configuration (separate implementation), or for protocol-agnostic network anomaly detection.


## 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

- Network TAP/SPAN on DNP3 communication segments (TCP port 20000 or serial)
- Baseline of normal DNP3 traffic patterns (masters, outstations, poll intervals, function codes)
- Suricata or Zeek with DNP3 protocol parser enabled
- Understanding of DNP3 function codes and object groups used in the environment
- DNP3 communication topology map (master-to-outstation relationships)

## Workflow

```python
# 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 extract_iocs(text: str) -> dict:
    return {k: re.findall(v, text) for k, v in IOC_PATTERNS.items()}
```

1. **Define Detection Scope** — Identify the specific dnp3 protocol anomalies techniques or indicators to hunt. Map to MITRE ATT&CK tactics/techniques where applicable.
2. **Collect Baseline Data** — Gather historical logs and establish normal behavior patterns for dnp3 protocol anomalies.
3. **Build Detection Queries** — Write detection rules, Sigma rules, or SIEM queries targeting dnp3 protocol anomalies indicators.
4. **Execute Hunts** — Run queries against the collected data, starting with broad filters and narrowing down.
5. **Triage Results** — Investigate alerts, filter false positives, and validate findings against known-good behavior.
6. **Document Findings** — Record confirmed detections, IOCs, and affected systems. Update detection rules based on findings.

## Tools

- **SIEM Platform** — Central log aggregation and query execution
- **Sigma Rules** — Vendor-agnostic detection rule format
- **MITRE ATT&CK Navigator** — Technique mapping and coverage analysis


## Process

1. **Reconnaissance** — Gather target information, identify attack surface, enumerate services
1. **Analysis/Exploitation** — Execute the technique, analyze results, document findings
1. **Reporting** — Document IOCs, write findings, provide remediation recommendations

## Verification

- [ ] All dnp3 protocol anomalies procedures executed completely and documented
- [ ] Findings validated against multiple data sources
- [ ] False positives identified and filtered
- [ ] Results documented with evidence and timestamps
- [ ] Recommendations provided with risk-based prioritization

## Anti-Rationalization Table

| Rationalization | Reality |
|---|---|
| "We are too small to be targeted" | Automated attacks target everyone. Size does not matter. |
| "Security slows us down" | A breach slows you down 100x more. Build security in from the start. |
| "We will fix it after launch" | Vulnerabilities in production are exploited within hours. Fix before deploy. |