---
title: "Attack Surface Reduction (ASR) Policies in Intune"
canonical: "https://kb.uconn.edu/space/IKB/27919253531/Attack%20Surface%20Reduction%20(ASR)%20Policies%20in%20Intune"
format: markdown
---
Beginning **September 2025**, Information Technology Services (ITS) will roll out Microsoft Defender **Attack Surface Reduction** (ASR) policies to all Windows devices managed in Intune.  
ASR rules harden PCs by blocking or auditing behaviors that malware frequently abuses—such as Office macros spawning scripts or credential-stealing attacks—*before* traditional antivirus signatures even come into play.

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## **Why we’re doing this**

| Goal | Benefit to the organization |
| --- | --- |
| **Reduce zero-day risk** | ASR rules target entire classes of attack techniques, not single CVEs. |
| **Meet Microsoft “Standard Protection” baseline** | Defender’s security baseline now flags several ASR rules as *required* for basic protection. |
| **Streamline incident response** | Fewer successful exploits mean fewer tickets and faster containment for SOC/IRT teams. |

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## **Scope & Audience**

- **Primary:** Desktop Engineering, Security Operations, Intune administrators
- **Secondary:** Power users & general staff who may notice new block or warning pop-ups

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## **Roll-out Plan**

> All phases will be monitored through **Defender Security Center → Incidents & alerts** and **Intune Endpoint Analytics** dashboards. Feedback loops with local IT contacts are baked into each step.

| Phase | Target devices | Mode | Notes |
| --- | --- | --- | --- |
| **0 – Pilot (complete)** | 50 ITS workstations | Audit | Validated logging & exclusions |
| **1 – ITS & Shared Spaces** | - All ITS Employee Devices
- Classroom/lab PCs
- Conference-room PCs | Audit → Block | Three-week soak in Audit, then flip to Block |
| **2 – Campus Group A** | Random ⅓ of colleges/departments | Audit → Block | Composition chosen by Intune dynamic group (deviceId mod 3 = 0) |
| **3 – Campus Group B** | Next random ⅓ of units | Audit → Block | Same 21-day cadence |
| **4 – Campus Group C** | Final ⅓ of units | Audit → Block | Completes full population |

*Dates may shift if telemetry reveals unexpected application impact.

### How the groups are built

- **Randomized assignment:** Devices are auto-tagged into *Group A/B/C* via an Intune dynamic rule that hashes the device ID; this prevents bias toward any single department.
- **Staggered 21-day windows:** Each group spends three weeks in **Audit** so Desktop Engineering can review logs and add exclusions before the automatic switch to **Block** mode.
- **Communication cadence:**
  - **T-7 days:** Heads-up email to local IT contacts and unit leadership
  - **T-0:** Post in Daily Digest
  - **T + 0–7 days (Audit)**: Daily telemetry review; high-noise rules adjusted or excluded
  - **T + 21 days:** Mode change to **Block** followed by intensified monitoring for two weeks

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## **What End Users Will Experience**

| Scenario | User prompt / action |
| --- | --- |
| Legitimate action blocked | A Windows Security toast: “This action was blocked by your IT administrator.” Clicking **Details** shows the rule name and a link to this KB. |
| Allowed via *Warn* mode (future enhancement) | A dialog offering **Unblock** (grants 24-hour exemption) or **Cancel**. |
| No noticeable change | Most users won’t see anything unless their workflow triggers a rule. |

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## **Administrator Checklist**

1. **Confirm device readiness**  
*Windows 10 21H2 or later and Defender platform ≥ 4.18.2008.9 required.*
2. **Verify inclusion in correct group**  
*Endpoint security → Attack surface reduction → “ITS-ASR-Baseline”* and group tag.
3. **Review Audit telemetry** during the three-week soak period.
4. **Add exclusions** for business-critical apps if necessary.
5. **Switch to Block mode** on the scheduled date (automatic unless postponed).
6. **Monitor alerts** after Block activation; escalate sustained false-positives via Jira Service Desk.

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## **Troubleshooting / FAQs**

| Question | Answer |
| --- | --- |
| **An approved app is now blocked. What do I do?** | Open a Jira ticket with the ASR event ID, timestamp, and full file path. Device Management and Security can look into an exclusion |
| **Can I temporarily disable a rule for testing?** | Yes—Intune’s “Override” profile lets you set a rule to *Audit* for a device group. Use sparingly and time-bound the scope. |
| **Will ASR replace AppLocker or Defender Application Control?** | No; ASR complements allow-listing solutions by focusing on behavior, not file hash or path. |

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