Windows 10/11 and SMB guest access

Windows SMB change and how to lock down your Raspberry Pi with SMB3 encryption:

Windows 10/11 and SMB guest access
Starting with Windows 10 version 1709 (Fall Creators Update) and all Windows 11 releases, Microsoft disabled unauthenticated “guest” access over SMB2 and SMB3 by default to block insecure, unencrypted logons (MKS Technology Inc)
URL: https://support.microsoft.com/en-us/help/4046019/guest-access-in-smb2-disabled-by-default-in-windows-10-and-windows-server-2016

Configuring your Raspberry Pi for SMB3-only, encrypted shares
Samba ≥ 4.2 (your 4.17.12 build included) fully supports SMB 3.x and on-the-wire encryption (Server Fault)
URL: https://serverfault.com/questions/913504/samba-smb-encryption-how-safe-is-it

Replace your /etc/samba/smb.conf with this:

[global]
   workgroup = WORKGROUP
   netbios name = raspberrypi
   server string = Raspberry Pi SMB3 Encrypted
   security = user
   map to guest = never
   usershare allow guests = no
   guest account = nobody

   server min protocol = SMB3
   server max protocol = SMB3
   client min protocol = SMB3
   client max protocol = SMB3
   smb encrypt = required

[data]
   comment = Encrypted SMB3 Share
   path = /data
   browseable = yes
   writable = yes
   valid users = pi
   create mask = 0775
   directory mask = 0775

1. Prepare the share directory and permissions: sudo mkdir -p /data sudo chown pi:pi /data sudo chmod 775 /data
2. Add pi as an SMB user: sudo smbpasswd -a pi
3. Apply changes: sudo systemctl restart smbd

This forces only SMB 3.x connections with required encryption, and only user pi can connect (Server Fault)
URL: https://serverfault.com/questions/895570/how-to-configure-samba-to-work-with-windows-10-1709

Verifying your setup

• Run testparm on the Pi to check for syntax errors.
• On Windows, open PowerShell and run: Get-SmbConnection You should see Dialect 3.1.1, confirming an encrypted SMB 3 session (samba.org)
  URL: https://www.samba.org/samba/docs/4.15/man-html/smb.conf.5.html

With these steps, your Windows 10/11 systems stay locked against guest shares, and your Raspberry Pi serves its data only over encrypted SMB 3 connections.