Firewall system is a system that used to protect local computer network from unauthorized access or unwanted communication. Firewall can restrict access from internet to local network. In this field work, a firewall system is built using OpenBSD 3.8 operating system. There are four steps to design firewall system using OpenBSD operating system. First, defines rules and ports that can be accessed by users from outside network. Second, installs and configures OpenBSD operating system. Third, configures the packet filtering firewall based on the rules and ports defined at the first step. And finally, tests the firewall system. In this project, firewall system blocked all communication from outside to local network except communication using ftp, pop3, auth, hhtp, https, smtp, icmp, imap4, 8080, dan 8021 port.