As attacks on enterprise network grow more sophisticated and diverse like malware, Advanced Persistent Threats (APTs) etc.; companies need to rethink their network defense and entire enterprise risk management strategies. Security for that matter is not only about protecting the network, but also the data. This requires a combination of tactics, from securing the network perimeter to encrypting data on mobile, storage devices and on-transit. As security become more complex, businesses increasingly see a need for enterprise security strategies, and are also grappling with new issues created by growing mobility and anywhere anyplace anytime access 24/7 - these require that the network security gateway defense systems: firewalls, UMTs, SIEMs etc. - must be configured correctly to allow internal users and road-warriors access to the private network but disallow unauthorized users - is very critical. This training guide is extremely critical for small and medium-sized businesses (SMBs) who often lack the IT resources of large companies but who can do with open-source software based network defensed systems. This training guide will walk you through the network security best practices.