Hello @Irlydk ,
Teams tag is mainly focused on the general issue of Microsoft Teams troubleshooting. According to your description, your question is not in our support scope.The following suggestion is just for your reference:
Changing your password is the right step. It is also recommended to enable 2-factor authentication if it is not already enabled.
Please refer to the documentation on how to enable 2-factor authentication: https://support.microsoft.com/en-us/account-billing/turning-two-step-verification-on-or-off-for-your-microsoft-account-b1a56fc2-caf3-a5a1-f7e3-4309e99987ca#:~:text=Go%20to%20Security%20settings%20and,Follow%20the%20instructions.
However, since someone was able to sign in to your account, you should also check to see if any unexpected forwarding rules were created since that is a common tactic by hackers
Use inbox rules in Outlook.com
https://support.office.com/en-us/article/use-in...
Turn on or off automatic forwarding in Outlook.com
https://support.office.com/en-us/article/turn-o...
Finally, if you have used the same email address/password combination on any other important accounts (i.e. social media, Amazon, Paypal etc) - you would be well advised to change the password on those accounts as well since it's not a question of <IF> a hacker will check to see if they can gain access to those accounts but rather <WHEN>.
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