Store-and-forward buffering of packets is traditionally used in modern network devices such as switches and routers. But sometimes it is a significant obstacle to the quality of service improvement because the minimal packet delivery time is limited by the multiplier of the number of intermediate nodes by the packet transmission time in the channel. The cut-through transmission of packets removes this limitation, because it uses only the head of packet, which contains the destination address, for the forwarding decision. Thus, the cut-through technology of packets transmission has considerable opportunities for the quality of service improving. Models for the computing grid with the cut-through forwarding have been developed in the form of colored Petri nets. The model is composed of packet switching nodes and generators of traffic; it can be supplied with malefactor models in the form of traffic guns disguised under regular multimedia traffic. The present work is the further development of methods of the rectangular communication grids analysis for nodes performing the cut-through switching. The methods are intended for application in the design of computing grids, in the development of new telecommunications devices, and in intelligent defense systems. Preliminary estimations show that the cut-through technology inherits some of the negative effects, which are associated with the traditional store-and-forward delivery of packets. A series of simulations revealed conditions of blocking a grid with its regular traffic. The results are applicable in the intellectual detection of intrusions and counter-measures planning.