With growing needs for communication and commerce over computer networks and the internet, increasingly complex threats to computer systems are emerging . In order to ensure bussiness continuity, companies must protect themselves against such threats. With additional methods of protection in place, one of the solutions for midsized companies is the unified threat management appliances. With implementation of the unified threat management appliance, we are adding another set of functionalities to network security. Devices of this type, among basic network routing and switching capabilities, contain additional functionalities for advanced threat protection. This paper describes replacement of the Cisco ASA 5510 statefull firewall with unified threat management appliance Fortinet FortiGate 300D in the enterprise company with 250 workstations and internal users, 50 branch offices with their own server infrastructure and publicly available web services. The entire process of implementation, from device selection to the actual implementation, within the existing system is described below. We are connecting unified threat mananagement appliance to the key IT services and systems of the company and configuring basic networking functionalities and management access to the device. Branch offices are being connected to the virtual private network and the entire internet trafic is sent through the FortiGate unit. In order to facilitate smooth legitimate use of the IT system and to prevent illegitimate actions from internal and external users and potential attackers, advanced functionalities for protection against threats are set up. We are creating profiles for protection against malicious code, web filtering, intrusion protection system, protection against Denial of Service attack, inspection of encrypted network traffic and e-mail filtering and combining them into security and access policies. Reporting and alerting system is an important component of appliance through which it is possible to analyze events and security incidents. After implementation of the device, functional tests that evaluate the success of defense against threats will be carried out.