SMB1 Explained & Why Disable It in Windows 11

If you manage a Windows 11 PC or home network, you may have heard that SMB1 is a security risk and should be disabled. This article explains what SMB1 is, why it is still present on some systems, the specific dangers it poses, and how to disable it safely without breaking access to older devices.

What Is SMB1?

SMB (Server Message Block) is a network file-sharing protocol that lets computers share files, printers, and other resources over a LAN. SMB1 is the original version, introduced in the 1980s and widely used through Windows XP and early Windows 7. It was designed for a time when networks were small and security threats were less sophisticated.

Microsoft deprecated SMB1 years ago and removed it by default from Windows 10 and Windows 11. However, it can still be enabled manually, and some older devices or software may require it. The protocol itself is decades old and lacks modern encryption, authentication, and integrity checks, making it a serious liability on any modern network.

Why Is SMB1 Dangerous?

SMB1 is the protocol exploited by the WannaCry and NotPetya ransomware attacks in 2017. These worms spread automatically across networks by exploiting a vulnerability in SMB1 (EternalBlue). Even though Microsoft released a patch, many systems remained vulnerable, and the damage was extensive.

Beyond that specific exploit, SMB1 has fundamental design flaws:

No encryption – data is sent in plaintext, so anyone on the network can sniff it.
Weak authentication – it supports older, easily cracked authentication methods.
No integrity checking – an attacker can modify data in transit without detection.
Large attack surface – the protocol has many legacy commands that are hard to secure.

Modern SMB versions (SMB2 and SMB3) address these issues with encryption, better authentication, and mandatory signing. Keeping SMB1 enabled is like leaving a door open in a modern building because it was designed for a different era.

How to Check if SMB1 Is Enabled

Windows 11 does not enable SMB1 by default, but it might be turned on if you upgraded from an older system or manually enabled it for compatibility. To check whether it is active:

Open PowerShell as Administrator.
Run the command: Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol
Look at the State – if it says Enabled, SMB1 is on.

Alternatively, you can check in Windows Features (optionalfeatures.exe) and look for “SMB 1.0/CIFS File Sharing Support.� If the checkbox is ticked, it is enabled.

How to Disable SMB1 in Windows 11

Disabling SMB1 is straightforward, and you can do it via PowerShell or Windows Features. The PowerShell method is cleaner and works on all editions:

Open PowerShell as Administrator.
Run: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol
Restart your PC when prompted.

If you prefer the GUI:

Press Win + R, type optionalfeatures, and press Enter.
Uncheck “SMB 1.0/CIFS File Sharing Support.�
Click OK and restart.

After disabling, you can verify with the same check command – the state should show Disabled.

What Breaks If You Disable SMB1?

Disabling SMB1 will prevent your PC from connecting to older devices that only support SMB1. Common examples include:

Legacy NAS drives (pre-2012 models)
Older Windows XP or Windows 2000 machines
Some old network printers and scanners
Certain embedded devices or industrial equipment

If you have such a device, you may lose access to shared folders or printers. However, most modern devices support SMB2 or SMB3, so the impact is usually minimal. For older devices, consider upgrading firmware or replacing them, as they are likely insecure anyway.

Common Misconceptions

One common myth is that disabling SMB1 will slow down your network. In reality, SMB1 is slower than SMB2/3, so disabling it can actually improve performance. Another misconception is that you need SMB1 for home networks – that is rarely true. Almost all consumer devices from the last decade support SMB2 or higher.

Some users worry that disabling SMB1 will break file sharing with other Windows PCs. That is false – Windows 10 and 11 use SMB3 by default, and SMB1 is not needed for communication between modern systems.

Alternatives and Best Practices

If you have an older device that requires SMB1, the best practice is to isolate it on a separate VLAN or network segment, and only enable SMB1 temporarily when needed. Never expose SMB1 to the internet, and ensure it is behind a firewall.

For modern file sharing, use SMB3 with encryption enabled. In Windows 11, you can enforce encryption by running Set-SmbServerConfiguration -EncryptData $true in PowerShell. Also, keep your system updated, as Microsoft regularly patches SMB vulnerabilities.

Frequently Asked Questions

Is SMB1 enabled by default in Windows 11?

No, Windows 11 does not enable SMB1 by default. It is only present if you manually enabled it or upgraded from a system that had it on.

Can I disable SMB1 without breaking my network?

Yes, in most cases. If all your devices are from the last decade, they support SMB2 or SMB3, so disabling SMB1 will not affect them. Only legacy devices will lose access.

How do I know if a device uses SMB1?

You can check the device’s documentation or use network analysis tools. A simpler way is to try connecting after disabling SMB1 – if it fails, that device likely relies on SMB1.

Will disabling SMB1 remove the WannaCry vulnerability?

Yes, disabling SMB1 eliminates the protocol that EternalBlue exploits. However, you should still apply security patches and use a firewall for full protection.

Can I re-enable SMB1 later if needed?

Yes, you can re-enable it using the same PowerShell command with Enable-WindowsOptionalFeature. But only do so temporarily and with caution.

Does SMB1 affect gaming or streaming?

No, SMB1 is not used for gaming or streaming. Those applications use other protocols, so disabling SMB1 has no effect on them.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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