PACKET SNIFFING AND FABRICATION ON LAN

Abstract

Network security is a complicated subject, historically only tackled by well-trained and experienced experts. However, as more and more people become 'wired", an increasing number of people need to understand the basics of security in a networked world. Security in itself can involve two aspects i.e. enhancing security and breach of security. The latter implies transgressing of network security and this involves a lot of activities vis-a-vis programming like sniffing, spoofing, Denial-of-Service, connection hijacking, etc. The goal of these attacks is to access some resource that a machine should not provide to the attacker. In this dissertation we have designed a package for sniffing and fabrication of packets on a LAN. The packets are sniffed when a client makes a request to the server. During this process they exchange a set progression of messages as explained in the three-way handshake. The third party (unauthorized host), senses this request, and captures the required packets. The identification of the required packet is done by looking into the TCP header of each packet and capturing only the connection request packets. The next step is fabricating a packet. Fabrication of the captured packet involves looking into each header of the captured packet, extracting the required values and building a new packet with the extracted values. The fabricated packet is then injected into the network, directed to reach the client. The program is written in C language and runs on a 1.6 GHz Pentium IV Processor running under the Linux Environment.