Can Cortex XDR fully substitute for Microsoft Defender Attack Surface Reduction (ASR) rules?

[atief]

Hello Cortex XDR Community,

We are in the process of transitioning our endpoint security stack and are using Cortex XDR as our primary AV/EDR solution, with Microsoft Defender offboarded. Our goal is to have a single, fully functional security control plane within Cortex.

We have a detailed set of Microsoft Defender Attack Surface Reduction (ASR) rules configured via Intune, but they are currently ineffective because Defender has been completely offboarded. We understand that simply moving Defender to passive or active mode would reactivate these rules, but we want to avoid a hybrid configuration if possible.

Based on our internal analysis, we've mapped our 17 ASR rules to Cortex XDR's protection modules as follows:

• 14 rules are covered by equivalent Cortex XDR features:
  • Child Process Protection: For rules blocking Office apps, Adobe Reader, script engines, and communication apps from creating child processes.
  • Exploit Prevention (EPM): For rules blocking Office code injection, Win32 API calls from macros, and kernel-level exploits.
  • Ransomware Protection: For advanced anti-ransomware behavior monitoring.
  • Credential Theft Protection: For blocking LSASS credential dumping.
  • Behavioral Threat Protection (BTP): For detecting obfuscated scripts, PSExec/WMI lateral movement, and other malicious causality chains.
  • Malware Prevention & Device Control: For blocking untrusted USB executables and email-based threats.
• 2 rules are partially covered:
  • "Block abuse of exploited vulnerable signed drivers": We map this to Kernel Exploit Prevention and BTP, which block the exploitation technique, but we note Cortex lacks a direct, explicit vulnerable driver blocklist like Microsoft's.
  • "Block persistence through WMI event subscription": We map this to BTP for detecting malicious WMI activity, but we don't see a dedicated control for blocking WMI event subscriptions themselves.

My question to the community and experts is:

1. Is our mapping and the conclusion that Cortex XDR can serve as a full functional replacement for Defender ASR rules accurate and valid?
2. For the two partially covered rules, are there more specific configurations, sub-modules, or BTP rules we might have missed that could provide coverage closer to the original ASR intent?
3. In a best-practice deployment where Cortex XDR is the primary solution, is it recommended to keep Defender in passive mode for the ASR rules, or can we confidently rely on Cortex's native modules?

Thank you.

[ChrisDavila · Accepted solution]

1. I'm not familiar with Defender ASR, but cortex xdr provides protection for everything in your list. 
2. - XDR uses Microsoft's vulnerable driver list. You can choose to block the driver from loading, alert on it, or allow it (not recommended).
   - XDR's built in analytics and you can build your own custom BIOCs to detect and block behavior. 
3. Rely on Cortex XDR