Purple Teaming on a Budget: Free Tools and Frameworks That Actually Work

Your organization just spent six figures on security tools. Firewalls, EDR, SIEM — the works. But when a real attacker sends a spearphishing email with a malicious macro, does your SOC actually detect it? If you can’t answer that question with data, your security program has a blind spot. Purple teaming fills that gap — and you don’t need a single paid license to get started.

TL;DR

• Purple teaming combines red team attacks with blue team detection — testing what you actually catch
• Five free tools cover the entire workflow: Atomic Red Team (attacks), Caldera (automation), Wazuh (detection), Sigma (rules), VECTR (tracking)
• MITRE ATT&CK is the common language that ties everything together
• You can run your first purple team exercise in a single afternoon with a laptop and VirtualBox
• Start small: pick 5 ATT&CK techniques relevant to your threat model and test those first

Why This Matters for You

Most security teams operate in silos. The red team finds vulnerabilities and writes reports. The blue team monitors alerts and responds to incidents. They rarely sit in the same room, looking at the same screen, asking the same question: “Did we catch that?”

Purple teaming breaks that wall. It’s not a separate team — it’s a methodology where offense and defense work together in real time. The red side executes a technique, the blue side checks if their tools detected it, and together they fix the gaps.

The best part? The entire toolchain is free and open source.

The Purple Team Toolchain — Overview

Here’s what you need and what each tool does:

Think of it like a production line: ATT&CK tells you what to test, Atomic Red Team and Caldera run the tests, Wazuh and Sigma detect them, and VECTR tracks whether you passed or failed.

MITRE ATT&CK: The Common Language

Before running any tests, you need a shared vocabulary. MITRE ATT&CK provides exactly that — a knowledge base of adversary tactics, techniques, and procedures (TTPs) observed in real-world attacks.

ATT&CK organizes attacks into 14 tactics (the “why” — like Initial Access, Persistence, Lateral Movement) and hundreds of techniques (the “how” — like T1566 Phishing, T1053 Scheduled Task).

ATT&CK Navigator — Your Visual Map

The ATT&CK Navigator is a free web tool that lets you create heatmaps of your coverage. Color-code techniques by:

• Red: tested, not detected (gap)
• Green: tested, detected (covered)
• Yellow: partially detected
• Gray: not yet tested

This single visualization becomes the centerpiece of every purple team exercise. It shows your CISO exactly where the gaps are — no PowerPoint needed.

Picking Your First Techniques

Don’t try to test all 200+ techniques at once. Start with the most common ones seen in your threat landscape:

# High-priority techniques for most organizations
T1566.001 - Phishing: Spearphishing Attachment
T1059.001 - Command and Scripting: PowerShell
T1053.005 - Scheduled Task/Job: Scheduled Task
T1003.001 - OS Credential Dumping: LSASS Memory
T1021.001 - Remote Services: Remote Desktop Protocol

These five techniques appear in nearly every major breach report. If you can detect these, you’re ahead of most organizations.

Atomic Red Team: Your Attack Library

Atomic Red Team is a library of small, focused test scripts mapped directly to ATT&CK techniques. Each “atomic test” simulates one specific adversary behavior — no complex infrastructure required.

Why Atomic Red Team Works

Traditional red team engagements take weeks and cost thousands. Atomic tests take seconds and cost nothing. Each test is:

• Self-contained — runs with a single command
• Reversible — includes cleanup steps
• Documented — explains what it does and what to look for
• Cross-platform — supports Windows, macOS, Linux, and cloud

Getting Started

# Install the Invoke-AtomicRedTeam module v2.0.4 (PowerShell)
Install-Module -Name invoke-atomicredteam,powershell-yaml -Scope CurrentUser
Install-AtomicRedTeam -getAtomics

# List available tests for a technique
Invoke-AtomicTest T1059.001 -ShowDetailsBrief

# Run a specific test (e.g., PowerShell download cradle)
Invoke-AtomicTest T1059.001 -TestNumbers 1

# Clean up after the test
Invoke-AtomicTest T1059.001 -TestNumbers 1 -Cleanup

The Purple Team Workflow

Here’s how you use Atomic Red Team in a purple exercise:

1. Red side announces: “Running T1003.001 — LSASS credential dump”
2. Red side executes: Invoke-AtomicTest T1003.001 -TestNumbers 1
3. Blue side checks Wazuh/SIEM: “Did we get an alert?”
4. Together they document the result in VECTR
5. If no detection: write a Sigma rule, deploy it, re-test

Each cycle takes 10-15 minutes. In a full day, you can test 20-30 techniques.

MITRE Caldera: Automated Adversary Emulation

While Atomic Red Team runs individual techniques, MITRE Caldera chains them together into realistic attack scenarios. It’s a full adversary emulation platform with a web UI and a C2 (Command and Control) server.

What Makes Caldera Different

Caldera doesn’t just run scripts — it makes decisions. You define an adversary profile (a set of ATT&CK techniques), deploy an agent on a target machine, and Caldera autonomously executes the attack chain. It adapts based on what it discovers, just like a real attacker.

Key Features

• Adversary profiles — pre-built attack playbooks mapped to real threat groups (APT3, APT29, etc.)
• Autonomous execution — the agent decides which technique to run next based on the environment
• Plugin ecosystem — extends functionality (Stockpile for techniques, Compass for ATT&CK visualization)
• Blue team mode — Response plugin lets you define and test automated defensive actions
• Caldera for OT — new plugins for industrial control systems (Modbus, BACnet, DNP3)

Quick Setup (v5.1.0+)

# Clone and start Caldera (requires Python 3.8+)
git clone https://github.com/mitre/caldera.git --recursive
cd caldera
python3 -m venv venv && source venv/bin/activate
pip install -r requirements.txt
python3 server.py --insecure --build

# Access the web UI
# Default: http://localhost:8888
# Credentials defined in conf/local.yml

When to Use Caldera vs. Atomic Red Team

In practice, most purple teams use both. Atomic for quick spot-checks, Caldera for full adversary simulations.

Wazuh: Your Free SIEM

You can’t detect attacks without a detection platform. Wazuh is a free, open-source SIEM (Security Information and Event Management) that integrates directly with MITRE ATT&CK.

Why Wazuh for Purple Teaming

Wazuh isn’t just a log collector — it has built-in ATT&CK mapping. When an alert fires, Wazuh shows you which tactic and technique triggered it. This makes it trivial to compare your test results against your detection coverage.

Key Purple Team Features

• ATT&CK dashboard — visual matrix showing which techniques generate alerts
• Sysmon integration — deep Windows event logging (process creation, network connections, registry changes)
• File integrity monitoring — detects unauthorized file changes
• Active response — can automatically block attacks (for testing defensive automation)
• Custom rules — easy to add new detection logic in XML format

Mapping an Atomic Test to a Wazuh Alert

When you run Invoke-AtomicTest T1003.001 (LSASS dump), Wazuh should generate an alert like:

Rule: 92000 - Sysmon - Possible credential dumping
MITRE ATT&CK: T1003.001 - OS Credential Dumping: LSASS Memory
Level: 14 (High)
Agent: WIN-TARGET

If you don’t see this alert, your detection has a gap. Time to write a Sigma rule.

Sigma Rules: Vendor-Neutral Detection

Sigma is the “YARA for logs” — a generic signature format for SIEM systems. Write a detection rule once in Sigma’s YAML format, then convert it to any SIEM query language (Wazuh, Splunk, Elastic, Sentinel, etc.).

Why Sigma Matters

The Sigma repository on GitHub contains over 15,000 community-contributed rules covering a huge range of ATT&CK techniques. Instead of writing detection rules from scratch, you can:

1. Find a Sigma rule for the technique you’re testing
2. Convert it to your SIEM’s format
3. Deploy and validate

Anatomy of a Sigma Rule

title: LSASS Memory Access via Procdump
id: 5afee48e-67dd-4e03-a783-f74259dcf998
status: stable
description: Detects procdump accessing LSASS memory
references:
    - https://attack.mitre.org/techniques/T1003/001/
author: Florian Roth
date: 2024/01/15
tags:
    - attack.credential_access
    - attack.t1003.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains|all:
            - 'procdump'
            - 'lsass'
    condition: selection
level: critical

This rule triggers whenever a process is created with a command line containing both “procdump” and “lsass”. Simple, readable, and platform-independent.

Converting Sigma to Your SIEM

# Install sigma-cli and backends (use a virtualenv to avoid system package conflicts)
python3 -m venv sigma-env && source sigma-env/bin/activate
pip install sigma-cli pySigma-backend-splunk pySigma-pipeline-sysmon

# Convert to Splunk SPL
sigma convert -t splunk -p sysmon rules/windows/process_creation/proc_creation_win_procdump_lsass.yml

# Convert to Elasticsearch (Lucene)
pip install pySigma-backend-elasticsearch pySigma-pipeline-ecs-windows
sigma convert -t lucene -p ecs_windows rules/windows/process_creation/proc_creation_win_procdump_lsass.yml

Supported backends include Splunk, Elasticsearch, Microsoft Sentinel (KQL), QRadar, CrowdStrike LogScale, and more. You can also convert rules one at a time using sigconvert.io.

For Wazuh specifically, you’ll translate the Sigma detection logic into Wazuh XML rules manually or via community-maintained converters, then drop them into /var/ossec/etc/rules/local_rules.xml:

<!-- Example: Wazuh rule for LSASS access via Procdump -->
<rule id="100002" level="14">
  <if_sid>61603</if_sid>
  <field name="win.eventdata.commandLine" type="pcre2">procdump.*lsass</field>
  <description>Procdump accessing LSASS memory - credential dumping</description>
  <mitre>
    <id>T1003.001</id>
  </mitre>
</rule>

The Detection Engineering Loop

This is where purple teaming becomes detection engineering:

1. Test a technique with Atomic Red Team
2. Check if Wazuh catches it
3. If not: find a Sigma rule or write one
4. Convert the Sigma rule to Wazuh format
5. Deploy and re-test
6. Document in VECTR

Each iteration makes your detection coverage stronger. Over weeks and months, you build a comprehensive defense validated by actual testing.

VECTR: Tracking and Measuring Results

Running tests is useless if you don’t track the results. VECTR by Security Risk Advisors is a free platform that records every purple team test and measures your detection coverage over time.

What VECTR Tracks

• Test cases — individual ATT&CK techniques tested
• Detection status — detected, partially detected, not detected, or blocked
• Tools involved — which SIEM rule, EDR alert, or other tool caught it
• Campaigns — group tests into logical exercises (e.g., “APT29 simulation Q1 2026”)
• Trends — coverage improvement over time

Why Metrics Matter

“We did a purple team exercise” means nothing to a CISO. “We tested 47 ATT&CK techniques across 5 tactics. Our detection rate improved from 34% to 71% over 3 months” — that’s a story that gets budget approved.

Quick Setup

# VECTR runs as Docker containers
git clone https://github.com/SecurityRiskAdvisors/VECTR.git
cd VECTR
# Follow the install guide for Docker Compose setup
docker compose up -d

# Access at https://localhost:8081

Putting It All Together: Your First Exercise

Here’s a step-by-step plan for your first purple team exercise using only free tools:

Prerequisites (1-2 hours)

1. Target VM — Windows 10/11 with Sysmon installed and Wazuh agent reporting to your Wazuh server
2. Attack VM — Kali or any Linux with PowerShell Core and Invoke-AtomicRedTeam
3. Wazuh server — Docker or dedicated VM (4GB RAM minimum)
4. VECTR — Docker on any machine

The Exercise (4-6 hours)

Phase 1: Scope (30 min)

• Pick 5 ATT&CK techniques based on your threat model
• Create a campaign in VECTR
• Open ATT&CK Navigator and create a blank layer

Phase 2: Baseline (1 hour)

• Run each Atomic test without any custom detection rules
• Record what Wazuh catches out of the box
• Mark results in VECTR: green (detected), red (missed)

Phase 3: Fix Gaps (2-3 hours)

• For each missed technique, search the Sigma repository
• Convert matching Sigma rules to Wazuh format
• Deploy the new rules and restart Wazuh
• Re-run the Atomic tests

Phase 4: Document (30 min)

• Update VECTR with final results
• Update ATT&CK Navigator heatmap
• Screenshot the before/after coverage comparison

Phase 5: Report (30 min)

• Export VECTR metrics
• Note which techniques are still undetected and why
• Plan next exercise focusing on remaining gaps

Expected Results

A typical first exercise with 5 techniques:

• Before: 1-2 detected out of the box (20-40%)
• After: 4-5 detected with Sigma rules (80-100%)
• Time invested: One afternoon
• Cost: $0

Advanced Tips

Automate with Caldera

Once you’re comfortable with manual testing, set up Caldera to run adversary profiles on a schedule. Deploy agents on test VMs and let Caldera execute weekly simulations. Compare Wazuh alerts against Caldera’s operation log to find new gaps.

Build a Detection Rule Library

Every Sigma rule you write or customize becomes part of your organization’s detection library. Store them in a Git repository with CI/CD that automatically deploys to Wazuh when you merge a pull request.

Map to Real Threat Intelligence

Use threat intelligence reports to identify which APT groups target your industry. Load their ATT&CK techniques into Navigator and prioritize testing those specific techniques.

Integrate with Your EDR Solution

Purple teaming isn’t limited to SIEM. Run the same Atomic tests and check if your EDR catches them independently. This reveals overlaps and gaps between your security layers.

What You Can Do Today

1. Install Invoke-AtomicRedTeam on a test machine and run your first test — it takes 5 minutes
2. Deploy Wazuh with Docker if you don’t have a SIEM — the quick start guide gets you running in 30 minutes
3. Browse the Sigma repository on GitHub — find 3 rules relevant to your environment and convert them
4. Create an ATT&CK Navigator layer for your organization — even an empty one gives you a starting point
5. Schedule a 4-hour block with your red and blue team members for your first exercise

Purple teaming doesn’t require expensive tools or dedicated teams. It requires a mindset: test what you think you detect, fix what you don’t, and measure the improvement. Every tool in this guide is free. The only investment is your time — and it’s the highest-ROI security activity you can do.

Related Posts

• Antivirus vs EDR vs XDR — What’s the real difference in 2026? — Understanding the detection layers purple teaming validates
• What It Really Takes to Become a True SOC Professional — The skills that make purple team exercises effective
• The Digital Parasite: How Attacker Tradecraft Evolved in 2026 — Real-world TTPs you should test against
• C2 Without Owning C2: When Attackers Use Your Trusted Services — A technique category worth including in your purple team scope
• 218 Million Reasons to Worry: What Honeypot Data Reveals — Threat data that informs which techniques to prioritize

Sources

• MITRE ATT&CK Framework
• Atomic Red Team — GitHub
• MITRE Caldera — GitHub
• Sigma Rules — SigmaHQ
• Sigma Rule Repository — GitHub
• Wazuh Documentation — MITRE ATT&CK Module
• VECTR — GitHub
• ATT&CK Navigator — GitHub
• CISA — Atomic Red Team Resources