Data Protection Issues

How to Handle Virus Scanning for Azure Blob Storage and SharePoint REST Uploads

Steve K Oct 9, 2026 868 views

Question details

The user needs to determine if files uploaded to Microsoft SharePoint or Azure Blob Storage via REST APIs can be scanned for malware before or during the upload process.

How to Handle Virus Scanning for Azure Blob Storage and SharePoint REST Uploads

Product: Microsoft SharePoint and Azure Blob Storage
Device & OS: not provided
Scenario: Uploading application files to cloud storage environments using REST APIs and ensuring they are free from malware.
Observed behavior: Seeking a workflow, built-in solution, or API integration that successfully scans inbound files to maintain security protocols.

Before you start

Ensure you have administrator privileges in your SharePoint admin center or Microsoft Defender for Cloud settings to configure and review malware scanning policies.

Solution 1Recommended

Leverage Built-in SharePoint Malware Scanning

Use this solution to rely on SharePoint's native security features, which automatically process files uploaded through REST APIs.

SharePoint Online includes a built-in virus scanning engine that automatically checks files for malware. This protection extends to files uploaded programmatically via REST APIs.

Verify SharePoint Security Settings

Access the Microsoft 365 Defender portal to ensure that the Safe Attachments for SharePoint, OneDrive, and Microsoft Teams policy is enabled.

Upload Files via REST API

Continue using your REST API application to upload files. The upload will complete normally into the SharePoint document library.

Allow Asynchronous Scanning

Once uploaded, the SharePoint malware engine will asynchronously scan the file. If malware is detected, the file is immediately flagged, and user access is restricted.

Asynchronous Process: Because the built-in scan is asynchronous, the file is technically saved before the scan completes. However, SharePoint prevents downloads and sharing if a threat is found.

Solution 2

Configure Microsoft Defender for Azure Blob Storage

Apply this solution to enable native, cloud-based threat detection for files uploaded to Azure Blob Storage containers.

Solution 3

Implement a Dedicated Pre-Upload Scanning Middleware

Use this approach when strict compliance requires files to be scanned synchronously before they ever reach SharePoint or Azure Blob Storage.

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Frequently Asked Questions

Does SharePoint scan files synchronously during the REST API upload?

No, SharePoint's native malware scanning is asynchronous. The file upload completes first, and then the scanning engine processes it. If malicious, the file is immediately restricted so users cannot download it.

Can Microsoft Defender for Storage block malicious uploads in Azure?

Microsoft Defender detects malware upon upload and triggers security alerts, but it does not synchronously block the upload. You must configure automated response scripts, such as Azure Logic Apps, to delete or move the file after detection.

What happens if a user tries to download an infected file from SharePoint?

If SharePoint has flagged a file as malware, a shield icon appears next to it. Users without administrative privileges will be blocked from downloading, opening, or sharing the file.

Are there limits to SharePoint's built-in malware scanning?

Yes, SharePoint's built-in engine typically scans files asynchronously and has size limitations. Heavily encrypted files or password-protected archives cannot be effectively scanned by the default engine.

Microsoft Office Security Issues