Nowadays, the Internet touched every facet of modern life in terms of its usage and resources. Most of information based organizations like business organizations, governments and educational institutions are using the abilities of the Internet such as the ability to publish, ¿nd, communicate information with others. Thus, dependence on the information based organizations over the Internet is increasing day by day. However, most of the popular software contains flaws which are not only technically difficult, but also economically costly to be solved. These vulnerabilities and easy access to Internet resources are exploited by the intruders to misuse the Internet resources and launch in¿uential attacks against them. In this case, the detection of intrusions is very significant. Nature Inspired techniques, especially Genetic Algorithms have proved to be a promising direction for effective intrusion detection.