By default, a drag selection will select all components under the mouse. This can be a problem when viewing the scene in shaded mode since your selection may include components hidden from your view.
You can use Camera based selection to only select components with a clear line-of-sight to the camera. This ensures that you don’t accidentally select components you can’t see.
To select only unobstructed components
This is a global preference that turns on camera based selection for all of the transformation tools.
Maya only selects the components unobstructed by other components from the camera’s point of view.
Alternatively, you can also use the Automatic Camera based selection option in the Selection preferences, Common Selection Options, or the Modeling Toolkit to have Maya automatically turn Camera based selection on when viewing the scene in shaded mode, and turn it off when viewing in wireframe or X-Ray modes.