The Internet has become an integral part of human society and business, and its full potential is as yet untapped. Internet related crimes are rapidly on the increase, with numerous cases of people illegally accessing private networks. The vulnerability of such networks was underlined when a group of hackers going by the name "Milworm" gained access to the B.A.R.C servers sometime ago. These threats pose an unprecedented challenge to lawmakers and enforcers. Likewise this throws open a new arena of challenge for Network engineers and designers. A sophisticated array of security measures is being used to keep the hackers at bay.

           The first line of defense against external threats to networks is a "Firewall". In this paper we mainly want to focus on how to design a safe network using firewall and what are the different firewalls that are present.