Security services are one of the most desirable characteristics of the computational grids. Nowadays the swelling number of applications and consequent increase in the amount of critical data over the grids have considerably raised the stakes for an efficient security architecture. Establishing security solutions for computational grid remains in its initial stages, as there are a number of impediments in the way of successful implementation of these security designs on a real grid. Absence of suitable mechanism to simulate the various functionalities of grid security models is a major concern for security designers. A reliable simulator for the grid security services is indispensable so that the grid security solutions can be adequately tested before their implementation on a real grid. The available range of grid simulators does not provide any support for the security functions. This vacuity has overwhelmingly motivated us to develop the Grid Security Services Simulator (G3S).