Collective intelligence (CI) is shared or group intelligence that emerges from the collaboration, collective efforts, and competition of many individuals, and appears in consensus decision making. J. Berri proposed a framework for CI that aims to provide users with different applications to become aware with knowledge for their daily tasks. The framework exhibits four layers: web services management layer; knowledge management layer; application layer; and user layer. The chapter provides the general overview of CI with a discussion of how it can be effectively applied in different areas of computer networks. Passive CI systems can be used in almost any case where large groups of people already seem to exhibit collective-mind or swarm-resembling behavior, with each user performing individually but all users sharing a certain number of common goals. The chapter describes some relevant applications of collaborative filtering approach in computer network domain. It discusses some significant applications of genetic algorithms in Computer Network Domain.