Account Security Problems

How to Secure OneDrive After an Unauthorized Large File Is Added

Bushra Parveen Sep 29, 2026 869 views

Question details

The user needs to secure their Microsoft account and safely address an unrecognized, massive file that has been added to their OneDrive.

How to Secure Your OneDrive When an Unauthorized Large File Is Added

Product: Microsoft OneDrive
Device & OS: not provided
Scenario: A suspiciously large file has appeared in the user's Microsoft 365 or OneDrive account, and they cannot delete it due to a lack of ownership permissions, raising concerns about a potential security breach.
Observed behavior: An unauthorized large file is present in the account, deletion attempts fail because the user does not own the file, and the user suspects unauthorized account access.

Before you start

Do not open, download, or interact with the suspicious file in any way to prevent potential malware from executing on your device.

Solution 1Recommended

Secure Your Microsoft Account Immediately

Take immediate action to lock down your account if you suspect unauthorized access or a security breach.

If unfamiliar files are appearing in your cloud storage, it is crucial to revoke unauthorized access before investigating further.

Change Your Password

Navigate to the Microsoft Security Info page (mysignins.microsoft.com/security-info) and update your password to a strong, unique alternative.

Enable Multifactor Authentication

In your security settings, turn on Multifactor Authentication (MFA) to require a secondary verification step for all future logins.

Sign Out Everywhere

Select the option to sign out of all active sessions to instantly terminate any unauthorized connections to your account.

Secure Your Microsoft Account Immediately

Immediate Protection: Changing your password and forcing a global sign-out is the fastest way to block hackers from continuing to access your cloud storage.

Solution 2

Check Permissions and Request File Removal

Identify the origin of the file and contact the rightful owner or administrator to have it removed.

Solution 3

Report Malicious Files to Microsoft Support

Reach out to Microsoft Support if the file is malicious or if your personal account has been compromised.

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Frequently Asked Questions

Can a suspicious file in my OneDrive infect my local computer?

Generally, a malicious file sitting in your cloud storage cannot infect your local computer unless you actively download and execute or open it.

Why can't I delete a file located inside my own OneDrive?

The file is likely located in a shared folder where you only have 'View' permissions. In this scenario, only the original file owner or an administrator can delete it.

How do I sign out of all devices in Microsoft 365?

You can sign out everywhere by visiting the Microsoft My Sign-ins security info page (mysignins.microsoft.com), navigating to your account security settings, and selecting the option to sign out of all active sessions.

Will Microsoft Support help me remove a suspected Trojan from my account?

Yes, if you suspect a file contains malware and you cannot remove it yourself, contacting Microsoft Support or your organizational IT administrator is the recommended course of action.

Microsoft Office Security Issues