The way we worked them out was that they work by scanning the shields as they impact and remodulate to the shield frequency to bypass (similar to how you could modulate the phaser in the video game Star Trek DS9: The Fallen to bypass forcefields). They had a range limit because the further they went the more energy they lost and it diminished their calculation ability and response times.
They...remodulate something or other after
they explode, do they? Well, golly, the technobabble for that ought to fill another page of this thread.