My outlook has been hacked

Dear Barbora,

I'm sorry to hear about your issue. Hundreds of messages going out from your school address is a strong sign that the account itself has been compromised, which is why blocking the senders has not helped. Blocking only stops mail coming in, and it does nothing to stop someone who already has access to your mailbox. Unfortunately, as a forum moderator, I am not able to inspect your school account or its sign in activity to diagnose and fix this directly. My role here is limited to general guidance you can apply from your side.

The first thing to do is change your password through your school's official password reset page, ideally from a device you trust, and avoid reusing a password from any other account. After that, please contact your school IT team as soon as possible and ask them to treat this as a compromised Microsoft 365 account. Specifically, they should:

1. Temporarily block sign in if the spam is still going out
2. Revoke all active sign in sessions
3. Review and remove any unfamiliar MFA methods
4. Check recent sign in and audit logs
5. Remove suspicious inbox rules, forwarding addresses, delegates, and connected apps
6. Review the Sent and Deleted Items folders
7. Check whether Microsoft has restricted the account from sending mail

Unfamiliar sent mail, unknown forwarding, and inbox rules that hide or delete messages are all recognised indicators of a compromised Microsoft 365 mailbox, so those are worth flagging to IT directly.

If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support 

While you wait to hear back from them, turn on Microsoft Authenticator or another MFA method your school approves, sign out of Outlook, Teams, and OneDrive on any shared or unfamiliar devices, and run a full antivirus scan on your computer. Please do not open the attachments in those messages, and it is worth letting classmates and teachers know not to open anything unexpected coming from your address.

I hope this gives you a clear path forward. Should you have any further questions or need additional assistance, please don't hesitate to reach out. I'm always happy to help. Have a wonderful day! 

If the answer is helpful, please click "Yes" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

Note: Please follow the steps in the forum documentation to enable e-mail notifications if you want to receive the related email notification for this thread.