Can Defender for Endpoint block custom process behavior like CrowdStrike IOAs?
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MellowCedar47
I'm trying to determine whether Defender for Endpoint has an equivalent to CrowdStrike's Indicators of Attack that can block a specific behavior immediately, rather than only detect it afterward. For example, I'd like to prevent python.exe from running when its command line is launched from a user-writable path such as C:Users and ends with a .py file.
I can create custom detections, but those appear to trigger after the event and then perform response actions. Is there a Defender feature I'm overlooking for inline behavioral blocking, or does CrowdStrike provide a capability that Defender handles through separate application-control products?
Answers
Custom detections are based on Advanced Hunting queries and generally run after the activity has been recorded. They can trigger response actions such as isolating a device or quarantining a file, but they aren’t an inline execution-control mechanism, so they won’t reliably stop python.exe before it starts.
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The blocking function is handled by separate application-control technologies rather than the endpoint detection engine. Windows Defender Application Control or AppLocker can control execution based on policy, while Attack Surface Reduction rules provide blocking for a predefined set of behaviors. However, the exact combination of process name, user-writable path, and .py extension may not be expressible through the built-in ASR rules.
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There is a real capability gap, but it’s more accurate to describe it as a difference in product architecture than simply saying one detection engine is better. A custom behavioral block may be a single feature in one product, whereas the Microsoft approach splits detection, response, and execution control across different components. The practical test is to run the exact command in a controlled system and compare when the process is prevented versus when an alert appears. If the alert arrives only after execution, you have detection rather than prevention.
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MellowCedar47: That’s the issue I’m running into: we already use WDAC and AppLocker, but neither one gives us this particular contextual rule in the way we need.