How would I blur just a certain section of the scene, like a liscence plate that is moving around?

I think that Premiere has a mask tool that lets you select a portion of the film...then you can apply a blur plugin to just the selection. I know that after affects can do this but I am not sure about Premiere

Six+Plus Productions

Thats what I was thinking of doing but the car moves around the screen quite a bit so it would be a lot of work to change the garbage matte every couple of frames.

I have never used a mask tool in premiere if there is one, where is it and how do I use it?

Thanks