SharePoint Online, as part of its virus scanning processes, later determines if the file meets the criteria for a scan.A user uploads a file to SharePoint Online.In April 2018, we removed the 25 MB limit for scanned files. When a file is found to contain a virus, the file is flagged. The Microsoft 365 virus detection engine runs asynchronously (independent from file uploads) within SharePoint Online. What happens if an infected file is uploaded to SharePoint Online? For more information about strategies and best practices, see Security roadmap. We encourage all customers to investigate and implement anti-malware protection at various layers and apply best practices for securing their enterprise infrastructure. They aren't intended as a single point of defense against malware for your environment. The built-in anti-virus capabilities are a way to help contain viruses.
