# Impersonation protection checks SHOULD be used

Impersonation protection checks SHOULD be used. A Maester check for Exchange Online, Anti-phishing.

Source: https://maester.dev/docs/tests/CISA.MS.EXO.11.1

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<div class="test-byline"><div class="test-byline-avatars"><a class="test-byline-avatar test-byline-avatar--author" href="/contributors/soulemike" title="Michael Soule · Original author"><img src="https://github.com/soulemike.png" alt="Michael Soule" width="28" height="28" loading="lazy" decoding="async" /></a></div><div class="test-byline-meta"><span class="test-byline-text">Contributed by <a href="/contributors/soulemike">Michael Soule</a></span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/cisa">CISA</a> · Exchange Online · Anti-phishing · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId CISA.MS.EXO.11.1
```

## Overview

Impersonation protection checks SHOULD be used.

Rationale: Users might not be able to reliably identify phishing emails, especially if the `FROM` address is nearly indistinguishable from that of a known entity. By automatically identifying senders who appear to be impersonating known senders, the risk of a successful phishing attempt can be reduced.

#### Remediation action

1. Sign in to **Microsoft 365 Defender**.
2. In the left-hand menu, go to **Email & Collaboration** > **Policies & Rules**.
3. Select **Threat Policies**.
4. From the **Templated policies** section, select **Preset Security Policies**.
5. Under **Standard protection**, slide the toggle switch to the right so the text next to the toggle reads **Standard protection is on**.
6. Under **Strict protection**, slide the toggle switch to the right so the text next to the toggle reads **Strict protection is on**.

Note: If the toggle slider in step 5 is grayed out, click on **Manage protection settings** instead and configure the policy settings according to [Use the Microsoft 365 Defender portal to assign Standard and Strict preset security policies to users | Microsoft Learn](https://learn.microsoft.com/microsoft-365/security/office-365-security/preset-security-policies?view=o365-worldwide#use-the-microsoft-365-defender-portal-to-assign-standard-and-strict-preset-security-policies-to-users).

#### Related links

* [Defender admin center - Preset security policies](https://security.microsoft.com/presetSecurityPolicies)
* [CISA 11 Phishing Protections - MS.EXO.11.1v1](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/baselines/exo.md#msexo111v1)
* [CISA ScubaGear Rego Reference](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/Rego/EXOConfig.rego#L617)
* [Microsoft Learn - Impersonation settings in anti-phishing policies in Microsoft Defender for Office 365](https://learn.microsoft.com/defender-office-365/anti-phishing-policies-about#impersonation-settings-in-anti-phishing-policies-in-microsoft-defender-for-office-365)

## Details

<details>
<summary>Every attribute of this check</summary>

| Field | Value |
| --- | --- |
| Test ID | CISA.MS.EXO.11.1 |
| Severity | High |
| Suite | CISA |
| Product | Exchange Online |
| Related products | Defender |
| Feature | Anti-phishing |
| Area | Email and collaboration protection |
| Resource type | Tenant |
| User impact | Low |
| Implementation cost | Low |
| MITRE ATT&CK | T1566 Phishing, T1684.001 Impersonation |
| Supports benchmark | CISA SCuBA Secure Configuration Baselines for Microsoft 365 (version ScubaGear main, 2026-10-11), requirement MS.EXO.11.1 |
| Criticality | SHOULD |
| Upstream requirement | Moved to MS.SECURITYSUITE.2.1v1 (was MS.EXO.11.1v1) |
| Supports controls | cisa-scuba:MS.EXO.11.1, nist-800-53-r5:SI-8 |
| PowerShell test | [Test-MtCisaImpersonation](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.11.1.ps1) |
| Services | ExchangeOnline, Graph |
| Compatible licenses | ATP_ENTERPRISE |

</details>

## Source

- Test: [`tests/cisa/exchange/Test.CISA.MS.EXO.11.1.ps1`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.11.1.ps1)
- Documentation: [`tests/cisa/exchange/Test.CISA.MS.EXO.11.1.md`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.11.1.md)