The development of heterogeneous grid infrastructure is in its infancy and the potential impact of unauthorized network connections and/or potential system corruption is a serious concern. This project addresses the need for the integration of a dynamic firewall into a grid-enabled application environment. By its very nature, a grid-computing environment consists of a dynamic collection of applications, resources, and services that require access to network ports. The focus of this paper is on developing a dynamic iptables-based firewall that is capable of automatically identifying valid grid user/application network port connection requests and satisfying these requests based on a Globus proxy. The Dynamic Firewall (Dyna-Fire) service has been integrated into the Western New York's ACDC-Grid.