# SMB signing should be enabled on all domain controllers

SMB signing (also known as security signatures) is a security feature that helps prevent:

Source: https://maester.dev/docs/tests/AD-DC-04

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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/ad">Active Directory</a> · Active Directory · Domain controllers · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-DC-04
```

## Overview

SMB signing (also known as security signatures) is a security feature that helps prevent:

- **Man-in-the-middle attacks**: Attackers cannot modify SMB packets in transit
- **Session hijacking**: Ensures the integrity of SMB sessions
- **Replay attacks**: Prevents attackers from replaying captured SMB traffic

Without SMB signing, an attacker on the network could intercept and modify SMB traffic between clients and domain controllers.

#### Control Type

**Preventive**

#### Security Recommendation

**Enable SMB signing on all domain controllers.**

To enable SMB signing:
```powershell
#### Check current status
Get-SmbServerConfiguration | Select-Object EnableSecuritySignature, RequireSecuritySignature

#### Enable SMB signing
Set-SmbServerConfiguration -EnableSecuritySignature $true -RequireSecuritySignature $true -Force
```

You can also enforce SMB signing through Group Policy:
- Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options
- "Microsoft network server: Digitally sign communications (always)" = Enabled

#### How the Test Works

This test queries the SMB server configuration on each domain controller to check if SMB signing is enabled and required. It reports:
- Number of DCs with signing enabled
- Number of DCs with signing required
- Names of DCs without signing enabled

#### Related Tests

- `Test-MtAdDcSmbv1EnabledCount` - SMBv1 protocol status
- `Test-MtAdDcSmbv311EnabledCount` - SMBv3.1.1 protocol status

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-DC-04 |
| Severity | High |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Domain controllers |
| Area | Infrastructure hardening |
| Resource type | DomainController |
| User impact | Low |
| Implementation cost | Low |
| MITRE ATT&CK | T1557 Adversary-in-the-Middle |
| Supports controls | nist-800-53-r5:SC-8 |
| PowerShell test | [Test-MtAdDcSmbSigningEnabledCount](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DC-04.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Remoting:Microsoft.PowerShell, ActiveDirectory:Cim:root\Microsoft\Windows\SMB:MSFT_SmbServerConfiguration:Read |

</details>

## Source

- Test: [`tests/ad/domain-controller/Test.AD-DC-04.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DC-04.ps1)
- Documentation: [`tests/ad/domain-controller/Test.AD-DC-04.md`](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DC-04.md)