Legal Question in Landlord & Tenant Law in Virginia

No, it is not legal.

Well, maybe it is a little more complicated than that. The owners of the house can do what they want with their house, including installing cameras.

But they cannot USE those or any cameras to invade your privacy.

So to be technical they can modify their own house by installing cameras.

But if they turn the cameras on, they are invading your privacy, which can probably be handled either as a criminal violation or as a lawsuit. You can go to the "magistrate" who will be located at the Sheriff's office at the Fairfax adult detention center and ask them to swear out a warrant (criminal complaint).

Take photos of the cameras and show the pictures to the magistrate.

it is possible that the cameras are not in use. But that will be for the owners to explain.

And yes it can be an invasion of privacy even in the common areas but that might be more difficult to convince people of. The test is whether a "reasonable person" (normal or ordinary typical person) would have an "expectation of privacy" in the area being monitored.

Particularly because you were not told about it, you would have more reason to expect privacy in those areas.