Purple Teaming: Turning Red vs. Blue Into One Team

Proving you can be breached is not the same as getting better

A traditional red team engagement runs like a competition. Offensive specialists spend weeks trying to breach the environment while the defenders — ideally unaware — try to catch them. At the end, the red team delivers a report of how they got in, everyone winces, and the organization files it away. The exercise proves the obvious (a determined attacker can find a way in) and occasionally surfaces a critical flaw, but it rarely leaves the defensive team meaningfully better at detecting the next attacker. The knowledge stayed on the offensive side.

Purple teaming exists to fix that. It is not a third team — it is a way of working where the red team (offense) and blue team (defense) collaborate in real time, sharing knowledge as the exercise runs rather than only at the end. The red team executes a technique; the blue team watches their tooling to see whether it was logged, detected, and alerted; and together they close the gap immediately. The goal shifts from "can we get in?" to "can we detect and respond to this specific technique, and if not, why not?" It turns an adversarial test into a joint training exercise with a measurable output: improved detection coverage.

What each color actually does

The metaphor is worth grounding, because the roles are real and distinct even when they collaborate.

• Red team (offense). Emulates real adversaries — reconnaissance, initial access, privilege escalation, lateral movement, exfiltration. A good red team mirrors the tactics of threat actors who actually target your industry rather than showing off exotic tricks. Formal penetration testing and adversary emulation live here.
• Blue team (defense). The defenders who run detection and response day to day — SOC analysts, detection engineers, incident responders. Their job is to see the red team's activity in their telemetry and act on it.
• Purple teaming (collaboration). Not a standing team but a mode of operation. Red and blue sit together, the red operator announces or walks through each technique, and the blue team checks in real time whether their sensors saw it. When a technique goes undetected, they build and test a detection on the spot, then re-run the technique to confirm it now fires.

The color mixing is the whole idea: red plus blue produces purple, and the value is in the overlap where offensive knowledge directly improves defensive coverage.

Figure: purple teaming closes the loop in real time — each attacker technique is immediately checked against defensive telemetry, and any gap becomes a new, tested detection before the exercise moves on.

The mechanics of a purple team exercise

A productive purple team exercise is structured, not a free-for-all. The disciplined version runs roughly like this:

1. Pick objectives grounded in real threats. Choose techniques to test based on the adversaries relevant to your organization — typically framed against the MITRE ATT&CK matrix, so every technique maps to a catalogued tactic and you can talk about coverage precisely.
2. Execute one technique at a time, transparently. The red operator runs a specific technique — say, credential dumping or a particular persistence method — and tells the blue team exactly what they did and when. This is the opposite of a covert red team; transparency is the point.
3. Check detection at each step. The blue team looks at their SIEM, EDR, and other telemetry to answer three questions in order: Did we log the activity? Did we detect it (fire an alert)? Would we have responded appropriately? A "no" at any stage is a finding.
4. Close the gap immediately. When a technique is missed, the team diagnoses why — no telemetry, telemetry but no rule, a rule that should have fired but did not — and fixes it then and there, whether that means enabling a log source or writing a new detection.
5. Re-test to verify. The red team re-runs the technique to confirm the new detection actually fires. This verification step is what separates purple teaming from wishful tagging; a rule that exists is not the same as a rule that works.

The cadence matters as much as the mechanics. Purple teaming works best as a recurring practice — regular, focused sessions that steadily expand coverage — rather than a one-off event. Each session leaves behind concrete, tested detections and a clearer map of where the gaps still are.

Detecting is not the same as being covered

The most valuable and uncomfortable insight purple teaming delivers is the honest state of your detection coverage. Organizations routinely believe they can detect techniques that, when actually tested, sail through unnoticed. A rule tagged for a MITRE technique may cover only one narrow variant, or may have quietly broken when a log source changed format. You do not discover that from a coverage spreadsheet — you discover it when the red team runs the technique and nothing fires.

Purple teaming reframes coverage from a claim into a tested fact:

• Logged, detected, and responded are three separate bars. Activity can be logged but not alerted on, or alerted on but ignored. Each gap is different and needs a different fix.
• One detection is not coverage of a technique. Attackers have many ways to achieve the same objective. Testing multiple variants of a technique reveals whether your detection is robust or brittle.
• Detection health decays silently. Rules break when sources change; sources stop reporting. Recurring purple teaming catches the drift that a one-time assessment never would.

The output is a coverage map based on what actually fired, not what someone hoped would fire — which is exactly the input a mature security operations center needs to prioritize its detection engineering.

Where it fits alongside pen testing and red teaming

Purple teaming does not replace other offensive testing; it complements it, and the distinction guides when to use each.

• Penetration testing answers "what can an attacker exploit?" — finding and validating specific vulnerabilities and exploitable paths. It is essential for surfacing flaws.
• Red teaming answers "can we be breached, and how far can an attacker get undetected?" — a realistic, often covert, end-to-end test of people, process, and technology.
• Purple teaming answers "can we detect and respond to specific adversary techniques, and how do we improve where we can't?" — a collaborative, measurement-driven exercise that directly builds defensive capability.

A mature program uses all three: pen testing for vulnerability discovery, occasional red teaming for realistic end-to-end assessment, and regular purple teaming to systematically close detection gaps. Purple teaming is often the highest-return activity for a team that already has monitoring in place but is unsure how good it really is — and it upgrades the value of covert red team exercises, since the defenders it has trained are the ones facing the next real intruder.

Where to start

You do not need a large internal red team to begin. Start with a single focused session: pick a handful of high-priority ATT&CK techniques relevant to your industry, run them transparently against your environment, and honestly record which were logged, which were detected, and which were missed. Fix the gaps, verify the fixes by re-running the techniques, and schedule the next session. The compounding value comes from making it recurring, not from making the first one exhaustive.

intSignal runs purple team exercises that pair offensive penetration testing with hands-on detection engineering in your detection and response stack — mapping coverage against MITRE ATT&CK, closing gaps in real time, and verifying every fix actually fires. Talk to our security team and we will show you the difference between the detections you think you have and the ones that work.