What is the ruling on using the internet from Wi-Fi networks that are not password-protected, without the knowledge of their owners, and is that considered theft, knowing that this affects the speed of their connection, and does the ruling differ between knowing the owner of the network and not knowing them?

It is not permissible to benefit from internet service owned by others except with the owner's permission, due to the Hadith (definition): "Indeed, your blood, your properties, and your honor are sacred to one another." It is permissible to use public wireless networks installed by the state to serve people, as this constitutes a general permission. Therefore, one should verify whether the network is public or private.