Möglicher Fehler in Microsoft Defender für iOS: Der Webschutz verhindert den SMB-Zugriff über WireGuard-VPN

Hello,

I would like to report what appears to be a reproducible issue involving Microsoft Defender for Individuals on iOS, WireGuard VPN, and SMB file sharing.

Environment

• Microsoft Defender for Individuals (latest App Store version)
• Apple iPhone (latest iOS version)
• WireGuard VPN
• AVM FRITZ!Box 6690 Cable
• WD My Cloud EX2 Ultra NAS
• FE File Explorer Pro (SMB client)

Issue

When Web Protection is enabled in Microsoft Defender, SMB access to my NAS over an active WireGuard VPN tunnel consistently fails.

When Web Protection is disabled, SMB access immediately works again without changing any other settings.

The behavior is fully reproducible.

Steps to reproduce

1. Connect to the home network using WireGuard VPN.
2. Verify that the VPN tunnel is established successfully.
3. Open FE File Explorer Pro.
4. Try to access an SMB share on the NAS.
5. Access fails while Microsoft Defender Web Protection is enabled.
6. Disable only Web Protection in Microsoft Defender.
7. Retry the SMB connection.
8. Access succeeds immediately.

Expected behavior

SMB traffic should work normally through an established WireGuard VPN tunnel regardless of whether Microsoft Defender Web Protection is enabled.

Actual behavior

With Web Protection enabled:

• SMB host cannot be reached.
• Port 445 connection fails.
• FE File Explorer reports connection errors.

With Web Protection disabled:

• SMB access works immediately.
• No other configuration changes are required.

Troubleshooting already performed

The following has already been verified:

• WireGuard successfully establishes the VPN tunnel.
• Successful handshake is shown in WireGuard.
• Data is transmitted in both directions.
• The FRITZ!Box web interface is accessible through the VPN.
• The NAS is powered on and fully accessible from the local network.
• SMB permissions are correct.
• The issue only occurs when Microsoft Defender Web Protection is enabled.

Because all other components operate normally, the issue appears to be related to the interaction between Defender Web Protection and SMB traffic over an existing WireGuard VPN connection.

Questions

• Is this a known issue?
• Is SMB traffic intentionally filtered or inspected by Microsoft Defender Web Protection on iOS?
• Are there any recommended exclusions or configuration options for this scenario?
• Is this behavior expected or should it be considered a bug?

I would be happy to provide additional diagnostic information, screenshots, or test further configurations if that helps reproduce the issue.