Syed Naqvi Computer Sciences and Networks Department Ecole Nationale Supérieur des Télécommunications Paris, France Security and Trust for the Grids The grid computing paradigm offers both the availability of abundant computing resources, and the storage of increased amounts of valuable data. Such information systems heavily rely on the provision of adequate security. In the evolution of grids, security threats were overlooked in the desire to implement a high performance distributed computational system. But now the growing size and profile of the grid require comprehensive security solutions as they are critical to the success of the endeavor. A comprehensive security system, capable of responding to any attack on grid resources, is indispensable to guarantee its anticipated adoption by the enterprises and the general public. This talk will cover security and trust challenges for the grids; state of the art of grid security mechanisms; the concept of virtualizing security services and their pluggable implementation; and finally the simulations of grid security services.