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161: Attack surface reduction

Implementation Effort: High
User Impact: Medium

Overview​

Attack surface reduction in Intune covers multiple Windows hardening capabilities, including Microsoft Defender Attack Surface Reduction rules, exploit protection, device control, and application control-related settings. These controls reduce the ways malware, phishing payloads, and unauthorized software can execute or access data.

In Zero Trust, attack surface reduction matters because device trust is not only about enrollment and compliance. The device should actively prevent common post-compromise behavior such as credential theft, script abuse, malicious macros, and unapproved removable media usage.

Implementation Guidance​

Prioritize the control set​

  • Start with the controls that have the best security return and the clearest telemetry, especially Defender Attack Surface Reduction rules, exploit protection, and removable media controls.
  • Treat application control and strict device control as phased projects that require deeper app inventory and compatibility testing.
  • Map the target controls to business scenarios such as finance endpoints, developer workstations, kiosks, or shared devices.

Roll out safely​

  • Use audit mode where supported before enforcing high-impact rules so you can collect telemetry and tune exclusions based on evidence instead of assumptions.
  • Separate policy groups by risk and operational maturity rather than applying the strictest controls tenant-wide on day one.
  • Document approved exclusions with owner, justification, and expiration so that exceptions do not silently become permanent.

Operate with security monitoring​

  • Review Defender and Intune reports to identify blocked behaviors, noisy exclusions, and unsupported devices.
  • Coordinate with security operations so detections from ASR or device control can feed investigation workflows.
  • Reassess the policy set after major Windows releases and when Microsoft adds new rule coverage or changes recommendations.

Reference​