A 1.4 Megaton bomb was detonated at an altitude of about 250 miles over Hawaii in a test code named Starfish Prime. High energy particles trapped by the magneto sphere knocked out approximately 1/3 of the satellites orbiting at lower altitudes. It is theorized that there is a particularly vulnerable area where nuclear weapons can create man made Van Allen Belts. It would not be unrealistic to assume a few low level detonations could wipe out most of the satellites in low earth orbits. Hawaii also fell victim to EMP, approximately 300 street lights went out, alarms set off and power surges occurred in the electrical grid.
In short, anything inside or between the Van Allen Belts could be particularly nasty, however, they would only pose a threat to material. Beyond the Van Allen Belt the effects would be rather diminished owing to the blast effects being diminished over such a vast scale. Besides almost any viable nuclear deflection shot would likely occur well outside of the moons orbit.
Strip