Development of a distributed firewall using software defined networking technology Software defined networking (SDN) presents a new network architecture that separates the control logic of a network from its physical infrastructure. This allows for easy programmable networks without having to manually configure every network device individually. However, there are not much studies on security applications for SDN based networks. Hence, the goal of this work is to explore security possibilities by focusing on the development of a firewall prototype that maximizes the advantages of SDN. By building around the features of OpenFlow, an open SDN standard, a distributed flow-based firewall prototype was developed and tested on a simulated network through Mininet. The prototype was tested to show full functionality through ping tests in a distributed configuration without causing any delays in terms of latency.