No real way to protect it
1. Even if you use the Protect feature there are tools that will open up SWF's.
2. There is no way to prevent a SWF from being downloaded if it is on the web and available to the public. If you don't want the possibility of people stealing it then the only solution is to not make it public. This goes for anything on the web.
3. It is still possible (and easy) to rip the images from a SWF. The easiest way to rip a picture from a SWF is to use the [ALT] Prnt Scrn key while the Flash is playing. Then pasting into an image editor. There is no easy method of protecting any work from this.