You've come across a file in SharePoint Online, OneDrive for Business, or Microsoft Teams, but you are unable to open or share it. You can see the file is there, but it's blocked, as shown in the following example:
Read this article to learn why this is happening and what you can do.
Why is a file in SharePoint, OneDrive, or Microsoft Teams blocked?
The file is blocked to help protect you, your computer, and your organization from malware.
Certain safety features are in place in Office 365 such that a malicious file can be identified in SharePoint Online, OneDrive for Business, or Microsoft Teams. If a file in SharePoint, OneDrive, or Microsoft Teams is deemed malicious, that file is blocked so that no one can open or download the file. A blocked file has a marker after its file name, like this:
Although it can be inconvenient for a file to be blocked, getting infected with malware is even worse. Cybercriminals use ransomware, technical support scams, or unwanted software to compromise users and computers. Once cybercriminals get access to user credentials or sensitive information, they can use that information to gain access to more information or other users, or even charge fraudulent fees. To learn more, see Understand the different malware types.
What can I do to avoid running into malicious files in the future?
Although cybercriminals continue to find new ways to trick people with malware, there are steps you can take to help protect you and your computer.
Run security software on your computer and keep that software up to date. See Help protect my computer with Windows Defender.
Install the latest software updates on all your devices. See Windows Update: FAQ.
Use caution with email attachments and files. See How to recognize phishing email messages, links, or phone calls.
To learn more about how malware works and how to prevent malware infection, see Help prevent malware infection on your PC.
What do I do if I think the system made a mistake?
If a file is blocked that you think should not be, you will need some help from an Office 365 administrator who can research the issue and, potentially, unblock the file. To learn more about what Office 365 administrators do, see About Office 365 admin roles.