Predetermined islanding scenarios along with automated load shedding schemes are applied once a prospective cascading outage condition is predicted. If required, additional distributed generation at specified locations in the system is also determined. The choice of different islands along with loads to be shed is then made available to the operator so as to be armed for action in case the system security is compromised. Determination of line outages that lead to disastrous consequences, intentional islanding schemes, and load shedding schemes have been explored individually. A plan integrating these defense mechanisms coupled with the possibility of using distributed generation where and when available is presented via case studies. Results obtained from the application of this technique indicate that it can be a powerful approach for secure operation of power systems.