Purple Teaming: A Buyer's Guide to Joint Red-Blue Exercises

Who this is for

You're a security leader tasked with improving detection capability. You've read about purple teaming and see it pitched everywhere. But you don't know what to actually ask vendors for, whether you should hire external facilitators, or how to avoid spending a week on an exercise that doesn't move your security posture forward.

This guide is for teams evaluating a purple team engagement. It walks through what purple teaming is, what it isn't, the engagement formats that work, and how to measure whether you got your money's worth.

1. What purple teaming actually is (and isn't)

Purple teaming is red and blue working together to test and improve defenses before an attacker does. Red simulates attacks using ATT&CK techniques. Blue tries to detect them in real time. Then they swap notes, repeat, and ship detection content.

It is not a red team engagement with a debrief call afterward. Most "purple team exercises" we see are exactly that — red plants compromise indicators, blue doesn't catch them, then they sit down for an hour and red reads the report. Blue team members nod, take notes, and change almost nothing. That's not purple teaming; that's just a red team with a feedback loop that doesn't close.

Real purple teaming: red executes a technique. Blue hunts for it in real time using existing tools. If blue finds it, they document the detection and move to the next technique. If blue misses it, they analyze why (tooling gap, blind spot in visibility, tuning issue) and design a detection to catch it next time. Both pieces happen during the engagement, not in a report written after.

2. How it differs from a standard red team and from a tabletop

Red teams attack your infrastructure and defend with a report. Purple teams attack your infrastructure and iterate on your detection during the engagement. The difference is optionality — you can iterate or not. Most teams don't.

Tabletop exercises are all blue. Everyone sits around a table, you describe a scenario, and blue team members decide what they'd do in response. It's low-risk, requires no execution, and is almost entirely worthless for improving actual detection — tabletops measure what people say they'd do, not what your automation actually does.

Purple teaming is in the middle. Real execution. Real tooling. Real detections. But collaborative, not adversarial. Red is not trying to evade detection; red is trying to find the gaps that blue can't see yet.

3. The engagement formats

Workshop format (1–2 days): Select a narrow scope (identity attacks, lateral movement in the network, or supply chain compromise). Red and blue work through 3–5 ATT&CK techniques together in a controlled environment. Low cost, low risk, high learning. Best for teams new to purple teaming. You'll ship 2–3 detection gaps and maybe one piece of runbook content.

Sprint format (1 week): Red executes 10–15 techniques across your actual infrastructure. Blue hunts in production (or production-mirror) and ships detection content daily. Engagement model: red does technique, blue hunts, debrief meeting at EOD, blue ships detection if needed. This is the one that actually moves the needle.

Embedded format (2–4 weeks): Red sits in your SOC/SIEM room for an extended engagement. Blue hunts as red executes. Detection content ships as techniques complete. Better for larger teams with time to dedicate daily. Risk: becomes a red team engagement if blue is too busy to iterate on detections.

Continuous format (quarterly): Scheduled weeks of purple teaming every quarter. Requires the most discipline but gives you the best long-term detection improvement. Each quarter targets new ATT&CK techniques or environments.

4. ATT&CK technique selection

Start with your detection gaps, not your favorite attacker techniques. Everyone wants to test T1003 (credential dumping) because it's famous. But if you already detect it well, testing it again is wasted time. Instead:

Run a detection gap assessment first. Map your detection content against the techniques used by threat actors in your industry. Look for the holes. If you have weak or no detection for T1197 (BITS jobs), T1021.004 (SSH), or T1558 (Kerberos ticket abuse), start there.

Scoring matrix: For each high-relevance technique, score your detection maturity 1–5:

• 1: No detection (no rules, no hunting)
• 2: Ad-hoc detection (manual hunting, no automation)
• 3: Detection exists but high false-positive rate (tuning needed)
• 4: Detection works, low false positives (tested in exercise)
• 5: Detection works, tuned, integrated into alerting and response

Build your purple team technique list from all the 1s and 2s. You'll ship 3–4 new detections per technique, each validated by red executing it in your environment.

5. The day-by-day rhythm of a one-week purple team sprint

Monday: Kickoff. Scope and technique list locked. Red and blue teams establish communication channels (Slack, Discord, whatever). You define "detection success" — what does blue need to see to claim a win? (Log entry, alert, threat hunt finding?)

Tuesday–Thursday: Technique execution days. Each morning, red announces the day's technique. Red executes it on infrastructure. Blue hunts for it in real time using their SIEM, EDR, network monitoring, logs. EOD debrief: blue explains what they found or why they missed it. If a gap is found, blue owner writes a detection or tuning change and tests it before EOD.

Friday: Retests and report. Red re-executes any techniques blue missed on Tuesday–Thursday. Blue re-hunts with their new detections. Morning meeting: what worked, what didn't, technique list for next quarter's sprint.

By Friday EOD, you have a list of new detection content ready to ship to production. That's the only deliverable that matters.

6. Deliverables that actually matter

Ignore: PowerPoint slide decks, heatmaps of "detection maturity", recommendations lists. Those are noise.

You need:

• Detection content (Sigma, Yara, or your SIEM rule syntax). Every gap blue found gets a rule. Every rule gets tested against the technique red executed. Rules are versioned and checked into your detection repository.
• Gap matrix: Technique name, whether blue detected it, why (or why not), and which detection content was created. This becomes your detection roadmap.
• Retest results: On Friday, which techniques did blue catch the second time? This proves the detection improvement is real, not theoretical.
• Tuning changes: Any EDR, SIEM, or logging configuration changes needed to surface the data blue required to hunt. Specific commands, settings, and alerts.

7. The political dynamic

Red ego is the biggest threat to a purple team engagement. Red operators are used to being undetected. Now they're being hunted by blue with live feedback. If red doesn't handle that, they blame blue's tooling or ask to run "more advanced" techniques. They're avoiding admitting their technique was caught.

Blue defensiveness is the second threat. Blue team members are being tested publicly. If a detection fails in the debrief, they often retreat into "we don't have the tooling" or "that's too noisy to detect". Sometimes that's true. Sometimes it's a way to avoid building the detection.

You need a facilitator with authority to call both sides out. The facilitator's job is not to mediate; it's to make sure the exercise ships detection content, not excuses. That person should report to the CISO, not to the red team or SOC manager, so neither side can lobby them.

8. Metrics that prove ROI to leadership

The single best predictor of purple team ROI is whether the blue team ships detection content during the exercise, not after. If your detection ruleset is bigger and better at Friday EOD than it was Monday morning, the engagement worked. Measure it:

• Detection count: How many new rules or tuning changes shipped? (Target: 3–5 per 5-day sprint)
• Time to detection: How long did it take blue to spot the technique the second time (Friday retest)? Did it improve from Tuesday? (You want sub-5-minute detection for high-severity techniques.)
• False-positive rate: Run the new detections against a week of clean traffic. How many alerts are noise? (Tune until the rate is acceptable.)
• Technique coverage: What percentage of your industry-relevant ATT&CK techniques now have automated detection? (Track before and after.)

That's what you tell the board. Not "we ran a purple team exercise and improved our security posture" — that's meaningless. Say: "We ran a purple team sprint and shipped 12 new detection rules for high-priority ATT&CK techniques. Blue team detection time for lateral movement techniques dropped from 2 hours to 8 minutes. False-positive rate on new rules is 0.2%. Coverage of industry-relevant techniques increased from 64% to 71%." That's a metric.

The short version

Purple teaming is red and blue executing and hunting together during the engagement, not debriefing after. Most "purple team" exercises are red team engagements with a bad feedback mechanism — ignore those. Real purple teaming requires collaborative detection shipping, not recommendations. Start with a detection gap assessment, build your technique list from the 1s and 2s (no detection or ad-hoc hunting), and require a facilitator with CISO-level authority to keep both teams accountable. The only metric that matters is detection content shipped during the engagement and validated by retesting. Measure coverage, time-to-detection, and false-positive rate. A five-day sprint should produce 3–5 new rules and measurable improvement in hunt time for high-priority techniques.