Bonk is a variant of the Teardrop attack, which targets not at crashing the attacked computer, but to trick simple port filter Firewalls, which accept also fragmented packets and thus to penetrate into the network being protected. During this attack, the UDP or TCP Header of the first fragment is overwritten by skillful choice of the fragment offset. Thereby, simple port filter Firewalls accept the first packet and the appropriate fragments while overwriting the first packet's header by the second fragment. Thus suddenly a permissible packet is created, which rather actually should be blocked by the Firewall.
Concerning this occurrence, the Firewall can itself either reassemble or filter only the wrong fragment (and all following), leading to the problems already indicated by either one of the other solutions above.