Abstract-Past few years the use of Internet and its applications has increased to a great extent. There is also an enormous growth in the establishment of computer networks by large, medium and small organizations, for data transfer and information exchange. Due to this huge growth, incidents of cyber-attacks and security breaches have also increased. Data on a network is transferred using protocols such as Hyper Text Transfer Protocol, which is very vulnerable. Many types of malicious contents are hidden in packets that are transferred over a network or system, which may can to get it slow, crash or buffer overflow etc. Thus it is very important to secure networks from such types of attacks. There are lots of mechanisms available but still they are not good enough because of dynamic environment. Such kind of attacks can be countered by applying appropriate policies on network edge devices like Adaptive Security Appliance, firewalls, web servers, router etc. Also the packets which are transferred between networks, they should deeply inspect for malicious or any insecure contents. In this paper firstly we would study Network security issues and available mechanism to counter them our focus would be on inspecting the HTTP packets deeply by applying policies on ASA. Finally we would use Graphical Network Simulator (GNS3) to test such a policy.

Due to rapid need of computer's in business and other organizations many networks has been established. In today scenario attacks on computer networks has increased to a great extend. Networks are very much needed but they are very prone to attacks because of security breaches & vulnerabilities in traditional establishments. There are many types of attacks which can be penetrated in our networks or edge devices; one of the most prone attack is the ICMP flood attack leading to denial of service. In this paper we would analyze different types of DOS attacks and available mechanism to protect our network. Further we describe the need of establishment of secure computer networks by using proper policies, rules on edge network devices. We also have tested them in Lab using GNS3 simulator. By implementing enhanced policies internal network's can be secured from attacks like ICMP flood.