Breach and Attack Simulation (BAS): What It Is and How to Deploy It

Breach and attack simulation (BAS) is an automated, continuous method of testing your security controls by safely emulating real attacker behavior — malware execution, lateral movement, data exfiltration — against your live environment. Unlike a once-a-year penetration test, BAS runs on a schedule, maps each simulated action to a known adversary technique, and tells you exactly which detections and preventions fired and which failed. The goal is simple: prove whether your defenses actually stop the attacks you claim they stop.

What breach and attack simulation actually does

A BAS platform deploys lightweight agents (or uses agentless connectors) that execute controlled attack actions, then measures the outcome. A typical run answers three questions:

• Did the control prevent it? Did EDR quarantine the dropped payload, or did the firewall block the C2 callback?
• Did the control detect it? If it wasn't blocked, did your SIEM generate an alert and did the SOC see it?
• How long did it take? Mean time to detect (MTTD) per technique, not just per incident.

The critical differentiator from vulnerability scanning is that BAS tests behavior, not just missing patches. A fully patched host can still let ransomware encrypt files if your EDR's behavioral rules are misconfigured — BAS catches that gap.

Why MITRE ATT&CK is the backbone of BAS

Almost every serious BAS solution organizes its test library around MITRE ATT&CK, the industry-standard knowledge base of adversary tactics and techniques, which catalogs 14 tactics and over 200 techniques observed in real-world intrusions. This matters for two reasons.

First, it gives you a shared vocabulary. When a BAS run reports that you failed T1055 (Process Injection) or T1486 (Data Encrypted for Impact), your red team, blue team, and CISO are all pointing at the same square on the same map. Second, it lets you build coverage heatmaps: a green-to-red grid showing which of the 14 tactics you can reliably detect and which are blind spots. That heatmap becomes your prioritization engine — you fix the red columns that map to techniques your actual threat actors use.

This is why the "7 layers of security" framing (physical, network, endpoint, application, data, identity, and human/policy) is useful but incomplete for BAS planning. ATT&CK cuts across those layers by attacker intent, which is far more actionable when you're deciding what to test next.

Open-source BAS vs. commercial platforms

You don't need a large budget to start. Several credible open-source options let you run real technique emulation:

• MITRE Caldera — an automated adversary emulation platform built directly on ATT&CK by MITRE itself.
• Atomic Red Team — a library of small, discrete tests mapped to individual ATT&CK techniques; ideal for validating one detection at a time.
• Infection Monkey — automated breach simulation focused on lateral movement and network segmentation.

Commercial platforms (the category Gartner tracks in its research on security validation) add continuous scheduling, cloud and SaaS attack scenarios, automated reporting for auditors, and integrations that push findings straight into your SIEM and ticketing. The honest trade-off: open-source gives you depth and control but requires engineering time to operate; commercial gives you coverage breadth and executive-ready reporting with less overhead.

A simple BAS deployment template to start this quarter

Skip the boil-the-ocean approach. Use this prioritized rollout:

• Week 1 — Scope one segment. Pick your highest-value asset group (e.g., domain controllers or the finance segment). Don't run BAS across everything at once.
• Week 2 — Test the techniques that hurt. Start with the ATT&CK techniques tied to ransomware: Initial Access (T1566 Phishing), Execution, Credential Access (T1003 OS Credential Dumping), and Impact (T1486). These are the ones most likely to end up in a real incident.
• Week 3 — Measure prevention AND detection separately. A block is good; a block with no alert is a silent gap you'll regret during a real breach.
• Week 4 — Fix, re-run, and track the delta. The only metric that matters is whether your coverage heatmap turned greener between run one and run two.

As for "is there a major cyber attack going on right now?" — the operational reality is that there always is. BAS exists precisely because attacks are continuous, so your validation should be too. A control you tested six months ago may have drifted out of policy after a single agent upgrade.

If you want to see how specific ATT&CK techniques play out against a set of defenses before you commit to a full BAS program, try PlayCISO's free Attack Simulator to walk through realistic attack chains and spot your likely blind spots.