today the "default" password (the one which refresh every session) changed for no reason, i wasn't able anymore to connect to my remote computer but i didn't rebooted my pc or team viewer cliente. I'm afraid it could be some kind of "hacker" which accessed my PC.
Is this possible or there could be some other reason because my password refreshed?
The temporary password will refresh when TeamViewer is restarted. If TeamViewer is set to automatically check for updates (I think that's the default) it may have restarted the program.
You check C:\Program Files (x86)\TeamViewer\Connections_incoming.txt if you thing your computer was accessed.