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

Breach and attack simulation (BAS) is automated software that safely imitates real attacks inside your own environment to check whether your security controls work. A BAS tool runs known attacker techniques, such as a malicious attachment, a credential theft attempt or data being sent to an outside server, and records whether your email filter, endpoint protection, firewall or monitoring stopped it, detected it or missed it. Because it runs on a schedule, it shows when a control that worked last month has quietly stopped working. For related terms, see the cyber security glossary.

What is breach and attack simulation?

BAS is a category of security tool for continuous control validation. Instead of asking “what vulnerabilities do we have?”, as a scanner does, it asks “if an attacker did this, would our defences notice?” Most products map their simulations to MITRE ATT&CK, the public knowledge base of adversary tactics and techniques, so results can be read as coverage: which techniques are blocked, which are detected and which pass unseen.

It fills a gap between two familiar activities. A vulnerability scan lists weaknesses but never checks whether your defences would catch someone using them. A penetration test does, but only on the days the tester is working. BAS repeats the defensive check automatically, as often as every day.

How do breach and attack simulation tools work?

Most breach and attack simulation tools rely on lightweight agents installed on a sample of machines in different parts of the network, plus hosted components that play the outside attacker. A central console picks scenarios from a library, runs them on a schedule and compares the outcome with what your controls should have done.

The strength of BAS is repetition. A firewall rule change, an expired licence or an endpoint agent that stopped updating can undo a control silently, and a scheduled simulation catches that within days rather than at the next annual test.

What types of BAS tool are there?

Products differ in where the simulations run and which controls they check. Many combine several types in one console:

Whatever the type, the most useful check is often the last one: did each simulated technique produce the alert your security team expects to see? A technique that is logged but never alerted on is, in practice, missed.

BAS vs penetration testing vs red teaming

All three test your defences against attack techniques, but they answer different questions and suit different stages of maturity.

Organisations that use BAS still need penetration testing and, once their defences are mature, red team assessments. A useful pattern is to turn each finding from a human-led test into a BAS scenario, so the fix is checked automatically from then on. In a purple teaming exercise, attackers and defenders work through techniques together, and BAS can keep re-checking the detections they tune.

Some products sold under the BAS label also run automated penetration testing. Instead of replaying a fixed library of safe simulations, they try to exploit real weaknesses they discover, such as weak credentials or misconfigured services, and chain them into attack paths. That is closer to a penetration test, but it still follows programmed logic: it will not reason about the business logic of a bespoke application or judge what a finding means for your business. Our guide to penetration testing as a service covers where automated testing fits.

What is assumed breach testing?

Assumed breach testing starts from the position an attacker would have after a successful intrusion, typically a standard user account on a company laptop, instead of from outside. It accepts that a determined attacker will eventually get a foothold, through phishing or a stolen password, and spends the testing time on what matters next: privilege escalation, lateral movement, access to sensitive data and whether your monitoring notices.

BAS tools apply the idea automatically by running their simulations from agents already inside your network. Human-led assumed breach tests go further, because a tester adapts to what they find; an internal penetration test that starts from a standard user account is the most common form.

Where does BAS fit with CTEM?

In a continuous threat exposure management (CTEM) programme, BAS belongs to the validation stage, alongside penetration testing and red teaming. It answers part of the validation question, “would our controls stop or detect this?”, quickly and repeatedly, while human testing answers the rest: whether an exposure can actually be exploited and where it leads. BAS results also feed prioritisation, because an exposure your controls would not catch deserves more urgent attention.

What are the benefits of breach and attack simulation?

• Control drift is caught early. A security setting that stops working after a change shows up at the next scheduled run, not at the next annual test.
• Detection rules are tested, not assumed. Each simulated technique shows whether the alert your security team relies on actually fires.
• Fixes are confirmed automatically. Re-running the same scenario after a change shows whether the gap has closed.
• Coverage becomes measurable. Results mapped to attack techniques show which ones are blocked, detected or missed, which helps decide where security spending goes next.

What are the limits of breach and attack simulation?

• It only tests what is in its library, so it will not find a flaw in your own application or a misconfiguration nobody has written a scenario for.
• It needs agents and upkeep, and its coverage is only as good as where those agents are deployed.
• A “blocked” result in one place does not prove the same technique is blocked everywhere.
• It does not replace the penetration tests required by standards such as PCI DSS, and it rarely tests people or physical security.

Why Sovereign Secure?

BAS checks that controls keep working; our part is the human-led testing that finds what a simulation library cannot. Sovereign Secure provides penetration testing services, internal tests that start from a standard user account, and red team assessments. We are a PCI SSC Qualified Security Assessor company and ISO 27001 certified, so findings are mapped to the standards you are assessed against.

Next step: request a penetration testing quote for an assumed breach or red team test.