Blog Post

Storage at Microsoft

7 MIN READ

Stop using SMB1

NedPyle

Microsoft

Apr 10, 2019

First published on TECHNET on Sep 16, 2016

Hi folks, Ned here again and today’s topic is short and sweet:

Stop using SMB1. Stop using SMB1 . STOP USING SMB1!

In September of 2016, MS16-114 , a security update that prevents denial of service and remote code execution. If you need this security patch, you already have a much bigger problem: you are still running SMB1.

The original SMB1 protocol is nearly 30 years old , and like much of the software made in the 80’s, it was designed for a world that no longer exists. A world without malicious actors, without vast sets of important data, without near-universal computer usage. Frankly, its naivete is staggering when viewed though modern eyes. I blame the West Coast hippy lifestyle :).

If you don't care about the why and just want to get to the how, I recommend you review:

Otherwise, let me explain why this protocol needs to hit the landfill.

SMB1 isn’t safe

When you use SMB1, you lose key protections offered by later SMB protocol versions:

Pre-authentication Integrity (SMB 3.1.1+). Protects against security downgrade attacks.
Secure Dialect Negotiation (SMB 3.0, 3.02). Protects against security downgrade attacks.
Encryption (SMB 3.0+). Prevents inspection of data on the wire, MiTM attacks. In SMB 3.1.1 encryption performance is even better than signing!
Insecure guest auth blocking (SMB 3.0+ on Windows 10+) . Protects against MiTM attacks.
Better message signing (SMB 2.02+). HMAC SHA-256 replaces MD5 as the hashing algorithm in SMB 2.02, SMB 2.1 and AES-CMAC replaces that in SMB 3.0+. Signing performance increases in SMB2 and 3.

The nasty bit is that no matter how you secure all these things, if your clients use SMB1, then a man-in-the-middle can tell your client to ignore all the above . All they need to do is block SMB2+ on themselves and answer to your server’s name or IP. Your client will happily derp away on SMB1 and share all its darkest secrets unless you required encryption on that share to prevent SMB1 in the first place. This is not theoretical – we’ve seen it. We believe this so strongly that when we introduced Scaleout File Server, we explicitly prevented SMB1 access to those shares!

As an owner of SMB at MS, I cannot emphasize enough how much I want everyone to stop using SMB1 https://t.co/kHPqvyxTKC

— Ned Pyle (@NerdPyle) April 12, 2016

US-CERT agrees with me, BTW: https://www.us-cert.gov/ncas/current-activity/2017/01/16/SMB-Security-Best-Practices

SMB1 isn’t modern or efficient

When you use SMB1, you lose key performance and productivity optimizations for end users.

Larger reads and writes (2.02+)- more efficient use of faster networks or higher latency WANs. Large MTU support.
Peer caching of folder and file properties (2.02+) - clients keep local copies of folders and files via BranchCache
Durable handles (2.02, 2.1) - allow for connection to transparently reconnect to the server if there is a temporary disconnection
Client oplock leasing model (2.02+) - limits the data transferred between the client and server, improving performance on high-latency networks and increasing SMB server scalability
Multichannel & SMB Direct (3.0+) - aggregation of network bandwidth and fault tolerance if multiple paths are available between client and server, plus usage of modern ultra-high throughout RDMA infrastructure
Directory Leasing (3.0+) - Improves application response times in branch offices through caching

Running SMB1 is like taking your grandmother to prom: she means well, but she can't really move anymore. Also, it's creepy and gross

— Ned Pyle (@NerdPyle) September 16, 2016

SMB1 isn’t usually necessary

This is the real killer: there are far fewer cases left in modern enterprises where SMB1 is the only option. Some legit reasons:

You’re still running XP or WS2003 under a custom support agreement.
You have old management software that demands admins browse via the so-called ‘network' aka 'network neighborhood’ master browser list.
You run old multi-function printers with old firmware in order to “scan to share”.

These will only affect the average business or user if you let them. Vendors are moving to upgrade their SMB2 support - see here: https://aka.ms/stillneedssmb1 For the ones who aren't, their competitors are. You have leverage here. You have the wallet.

We work carefully with partners in the storage, printer, and application spaces all over the world to ensure they provide at least SMB2 support and have done so with annual conferences and plugfests for six years. Samba supports SMB 2 and 3. So does OSX and MacOS. So do EMC, NetApp, and their competitors. So do our licensed SMB providers like Visuality and Tuxera, who also help printer manufacturers join the modern world.

A proper IT pro is always from Missouri though. We provide SMB1 usage auditing in Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2008 R2 (the latter two received via backported functionality in monthly updates several years ago) plus their client equivalents, just to be sure. That way you can configure your Windows Servers to see if disabling SMB1 would break someone:

Set-SmbServerConfiguration –AuditSmb1Access $true

On Windows Server 2008 R2 and Windows 7 you must edit the registry directly for this DWORD value, there is no SMB PowerShell:

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" AuditSmb1Access -Type DWORD -Value 1 –Force

Then just examine the SMBServer\Audit event log on the systems. If you have older servers than WS2012 R2, now is good time to talk upgrade. Ok, that’s a bit extortionist – now is the time to talk to your blue teams, network teams, and other security folks about if and where they are seeing SMB1 usage on the network. If they have no idea, they need to get one. If you still don’t know because this is a smaller shop, run your own network captures on a sample of your servers and clients, see if SMB1 appears.

Day 700 without SMB1 installed: nothing happened. Just like last 699 days. Because anyone requiring SMB1 is not allowed on my $%^&%# network

— Ned Pyle (@NerdPyle) September 13, 2016

Update April 7, 2017: Great article on using DSC to track down machines with SMB1 installed or enabled: https://blogs.technet.microsoft.com/ralphkyttle/2017/04/07/discover-smb1-in-your-environment-with-dscea/

Update June 19, 2017 - Group Policy to disable SMB1: https://blogs.technet.microsoft.com/secguide/2017/06/15/disabling-smbv1-through-group-policy/

Update June 30, 2017 - You have probably seen me announce this on twitter and in other public venues: Windows 10 RS3 (Fall Creators Update) and Windows Server 2016 RS3 have SMB1 uninstalled by default under most circumstances: https://aka.ms/smb1rs3 . The full removal has begun. Make sure you check https://aka.ms/stillneedssmb1 for products that may require updates or replacement to be used without the need for SMB1.

Update July 7, 2017: if your vendor requires disabling SMB2 in order to force SMB1, they will also often require disabling oplocks. Disabling Oplocks is not recommended by Microsoft, but required by some older software, often due to using legacy database technology. Windows 10 RS3 and Windows Server 2016 RS3 allow a special oplock override workaround now for these scenarios - see https://twitter.com/NerdPyle/status/876880390866190336 . This is only a workaround - just like SMB1 oplock disable is only a workaround - and your vendor should update to not require it. Many have by now (I've spoken to some, at least) and their customers might still just be running an out of date version - call your suppliers.

SMB1 removal isn’t hard

Starting in Windows 8.1 and Windows Server 2012 R2, we made removal of the SMB1 feature possible and trivially easy.

On Server, the Server Manager approach:

On Server, the PowerShell approach (Remove-WindowsFeature FS-SMB1):

On Client, the add remove programs approach (appwiz.cpl):

On Client, the PowerShell approach (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol)

On legacy operating systems:

When using operating systems older than Windows 8.1 and Windows Server 2012 R2, you can’t remove SMB1 – but you can disable it: KB 2696547- How to enable and disable SMBv1, SMBv2, and SMBv3 in Windows Vista, Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows 8, and Windows Server 2012

A key point: when you begin the removal project, start at smaller scale and work your way up. No one says you must finish this in a day.

Explorer Network Browsing

The Computer Browser service relies on SMB1 in order to populate the Windows Explorer Network (aka "Network Neighborhood"). This legacy protocol is long deprecated, doesn't route, and has limited security. Because it cannot function without SMB1, it is removed at the same time.

However, some customers still use the Explorer Network in home and small business workgroup environments to locate Windows computers. To continue using Explorer Network, you can perform the following steps on your Windows computers that no longer use SMB1:

1. Start the "Function Discovery Provider Host" and "Function Discovery Resource Publication" services and set them to delayed start.

2. When the user opens Network, they will be prompted to enable network discovery. Do so.

3. Now all Windows devices within that subnet that have these settings in place will appear in Network for browsing. This uses the WS-DISCOVERY protocol. Check with your other vendors and manufacturers if their devices still do not appear in this browse list after Windows devices appear; it is likely they have this protocol disabled or only support SMB1.

Note: we highly recommend you map drives and printers for your users instead of enabling this feature, which still requires searching and browsing for their devices. Mapped resources are easier for them to locate, require less training, and are safer to use, especially when provided automatically through group policy.

SMB1 isn’t good

Stop using SMB1. For your children. For your children’s children. Please. We’re begging you. And if that's not enough: SMB1 is being removed (fully or partially, depending on SKU) by default in the RS3 release of Windows and Windows Server. This is here folks: https://aka.ms/smb1rs3

- Ned “and the rest of the SMB team at Microsoft” Pyle

Updated Sep 02, 2020

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NedPyle

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Joined April 26, 2017

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21 Comments

JBJBJB
Copper Contributor
Feb 12, 2024
Makes zero sense that a device that would take smb3 and convert it to smb1 bi-directionally at the printer. Can't be that hard....could be implemented on a Pi Zero or similar.
MacDknife
Copper Contributor
Feb 12, 2024
Hi All!
I would like to throw a spanner in the works! Yes, I know that SMB1 is not a viable communications protocol. I have a My Passport external drive and have had them for many years, so I know I have to have SMB1 activated in the latest versions of Windows. I did not think this would be neccessary when I tried to connect my new Nitro laptop with resources on my PC.

On my PC I could see my laptop computer in Network (in Explorer), but not the other way around. I could see no computers at all sometimes not even my own laptop), while experimenting with file access, public and private network settings. It was not until I gave up after some hours and decided to go ahead and change the settings in SMB1 so I could connect the My Passport device, that everything in Network was displayed! Imagine my surprise - and then my dismay when I realised why.

Microsoft is already taking steps to remove SMB1, as they should according to my for all the right reasons, BUT because of this I also realised that I do NOT decide what protocol my devices use and NEITHER does Microsoft - the manufacturers do! After realising this I knew I had to get a new external drive that did not use SMB1, so I contacted some manufacturers. The one that answered me (SSK) said that unfortunately there is no present WiFi drive that does not use SMB1.

So, the way I see it - DO NOT PUT PRESSURE ON THE USERS - PUT PRESSURE ON THE MANUFACTURERS! They are the ones that have to adapt and change first. We, the users, can only adapt to the devices and protocols used. Yes, we can choose not to use WiFi devices or maybe change to bluetooth instead, but if that is not an option?.... Not only that, but I find it very strange that no newly manufactured devices from 2020 and moving forward does not have SMB2 or 3 and reached the market now in 2024!? SMB1 is over 30 years old, so what is the holdup?

(If there are manufacturers that actually do have external wireless drives/devices that use SMB2 and/or 3, then I apologize up front and would like to put in a request for an external drive - 2TB or larger)
: P
/MacD
GoonerDane
Copper Contributor
Dec 07, 2023
Yes, its not in my list, is there a way to install it manually ? Ideally version 2 or 3, because I read first version is not safe ?
Stupid to have bought a NAS server but being unable to comunicate with it.
erpmanila3w
Brass Contributor
Dec 07, 2023
In my Windows 10 SMB1 is gone, not in the features list, I bought a NAS server, and when trying to communicate with it I get the message that I can't because I don't have SMB 2, what can I do?

GoonerDane
you mean you don't see this SMB1 feature on the "Windows Features" list in your edition of Windows 10?

I have it listed on my Win10 Home 22H2, Win10 Pro 22H2 & Win10 LTSC 2021 v21H2 computers but not installed by default
napki1540
Copper Contributor
Jul 19, 2023
Zwykły domowy zjadacz chleba ma:
- router
- NAS (być może)
- drukarkę
- PC stacjonarny
- 1-3 laptopów
i chciałby te urządzenia po prostu zobaczyć w otoczeniu sieciowym Windows (xp, vista, 7, 10, 11)
NIE DA SIĘ.
Po przekopaniu się przez kilkaset porad i artykułów, przy amatorskim (ale przyzwoitym) poziomie wiedzy na temat, nasuwa się wniosek że trzeba wrócić do AMIGI lub PC486 z Windows 3.11
Windows ma kilkadziesiąt procent udziału w rynku.
Śmiem twierdzić że ponad 50% tego to zwykli zjadacze chleb, a nie firmy z setkami komputerów i wieloosobowym działem IT.
I co? I nic! Ich problemów NIE DA SIĘ rozwiązać.
Fajny artykuł. Poszerza wiedzę. Ale do niczego się nie przyda szarym zjadaczom chleba .
urządzenia się nie widzą i już. NIE DA SIĘ.
Tylko po co nam wszystkim fachowcy, którzy istnieją dla siebie.
JBJBJB
Copper Contributor
May 30, 2023
Yeah....I really need to throw away (and I mean that in the most literal sense) a perfectly fine $10k HP printer because everybody is too lazy to make an SMB work around. You guys make me see red every time you start preaching about how superior you are by not giving a くそ for the consumer. Hundreds of thousands of printers were affected, not just mine. MS and HP and several other printer manufacturers gave us this.....🖕
GoonerDane
Copper Contributor
May 30, 2023
In my Windows 10 SMB1 is gone, not in the features list, I bought a NAS server, and when trying to communicate with it I get the message that I can't because I don't have SMB 2, what can I do?
JBJBJB
Copper Contributor
Feb 03, 2023
SoftwareRespect

Try a PowerShell script...

https://ss64.com/nt/net-view.html
SoftwareRespect
Copper Contributor
Feb 03, 2023
Thank you, late to the game here, but I came-across a script today that has been relying on net view for a long time. Net View is a COMMAND LINE function/utility that millions of admins have relied on for 25 years. Therefore what is the COMMAND LINE replacement for net view? Micro$oft industry leaders seem to be out-of-touch.
RUMCAdmin
Copper Contributor
Sep 08, 2021
Ned, what is the replacement for the functionality we illiterate SMB1 users want and need? All I see is preaching from you and your professional fanboys.