# URL comparison with a block-list SHOULD be enabled

URL comparison with a block-list SHOULD be enabled. A Maester check for Exchange Online, Safe Links.

Source: https://maester.dev/docs/tests/CISA.MS.EXO.15.1

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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><a class="test-byline-avatar" href="/contributors/thomas-s-schmidt" title="Thomas Schmidt · Co-contributor"><img src="https://github.com/thomas-s-schmidt.png" alt="Thomas Schmidt" 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> with <a href="/contributors/thomas-s-schmidt">Thomas Schmidt</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 · Safe Links · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId CISA.MS.EXO.15.1
```

## Overview

URL comparison with a block-list SHOULD be enabled.

Rationale: Users may be directed to malicious websites via links in email. Blocking access to known, malicious URLs can prevent users from accessing known malicious websites.

#### 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 either **Standard protection** or **Strict protection**, select **Manage protection settings**.
6. Select **Next** until you reach the **Apply Defender for Office 365 protection** page.
7. On the **Apply Defender for Office 365 protection** page, select **All recipients**.
8. (Optional) Under **Exclude these recipients**, add **Users** and **Groups** to be exempted from the preset policies.
9. Select **Next** on each page until the **Review and confirm your changes** page.
10. On the **Review and confirm your changes** page, select **Confirm**.

#### Related links

* [Defender admin center - Preset security policies](https://security.microsoft.com/presetSecurityPolicies)
* [CISA 15 Link Protection - MS.EXO.15.1](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/baselines/exo.md#msexo151v1)
* [CISA ScubaGear Rego Reference](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/Rego/EXOConfig.rego#L813)

## Details

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

| Field | Value |
| --- | --- |
| Test ID | CISA.MS.EXO.15.1 |
| Severity | Medium |
| Suite | CISA |
| Product | Exchange Online |
| Related products | Defender |
| Feature | Safe Links |
| Area | Email and collaboration protection |
| Resource type | Tenant |
| User impact | Low |
| Implementation cost | Low |
| MITRE ATT&CK | T1566.002 Spearphishing Link, T1204.001 Malicious Link |
| Supports benchmark | CISA SCuBA Secure Configuration Baselines for Microsoft 365 (version ScubaGear main, 2026-10-11), requirement MS.EXO.15.1 |
| Criticality | SHOULD |
| Upstream requirement | Moved to MS.SECURITYSUITE.7.1v1 (was MS.EXO.15.1v1) |
| Supports controls | cisa-scuba:MS.EXO.15.1, nist-800-53-r5:SI-3 |
| PowerShell test | [Test-MtCisaSafeLink](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.15.1.ps1) |
| Services | ExchangeOnline, Graph |
| Compatible licenses | ATP_ENTERPRISE |

</details>

## Source

- Test: [`tests/cisa/exchange/Test.CISA.MS.EXO.15.1.ps1`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.15.1.ps1)
- Documentation: [`tests/cisa/exchange/Test.CISA.MS.EXO.15.1.md`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.15.1.md)