First hacked page on Facebook, then in my world, where digging to the problem to understand?

Hello.
The computer has been in the hands of the attacker, stood Windows 7, then was hacked classmates and the messages were sent.
Then upgraded to Windows 10, there was a tampering with the mail mail.ru and again the messages were sent.
What actions can help prevent such situations?
July 2nd 19 at 18:25
3 answers
July 2nd 19 at 18:27
Perhaps you have the same password on all resources.
Change passwords, keep the computer in the wrong hands, if it already did, remove the system, because it could be a bookmark, such as a keyboard interceptor that remembers everything you type on your keyboard and sends to the owner.
July 2nd 19 at 18:29
Change passwords, check your startup, if there's nothing there, then constantly monitor the task Manager to reveal the extra programs. Also you can check the settings almost and so on. password recovery - attackers can stick their addresses to restore.
July 2nd 19 at 18:31
Reinstall the system.

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