These droids are used by the Empire and various other factions as an early detection and warning device. They fly above the ground and fire with a laser that has roughly the same power as a standard Stormtrooper Rifle. The speed of these droids is nothing to worry about but you should be carfeul of the secondary explosion when they are destroyed.
Suggested Method of Attack - Explosives are fairly tough to aim correctly for these guys, so an accurate energy weapon is best. Speed in taking them out is a consideration because while they won't win any races the probe droids are still pretty accurate with their laser over long range. The Fusion Cutter is usually a reliable weapon for dealing with probe droids.