I think you mean 'lens flare'
Opening up the aperture will help,
ND filters, lens hood, although shooting directly into the sun won't help, some people think polarizing filters just make things worse, a good quality coated lens - failing that use your hand, hat or anything you find..
Often using a lens hood will help. Avoid having the disc of the sun visible in the frame, keep direct sunlight from striking the front of the lens. There isn't a filter that will prevent these "flying saucers". Only can be solved with good lens work and good craftsmanship.
In order to get the flare off your image you MUST keep direct sunlight, or any light source, from striking the front of the lens. Any time direct sunlight reaches the front of the lens and then shines into the lens, you will have lens flare, which reduces contrast and, or, UFO's in your image. No filter will get rid of it and changing your zoom lens only diminishes the effect.