Increasing need and use of internet is encouraging the development of new protocols, applications, services, etc. Even though these new developments are more robust than the previous ones, the network attacks are also emerging and are increasing security threat. The intrusion detection systems are not able to detect all types of attacks, so a solution to this problem is to combine some intrusion detection approaches to cope with the attacks effectively. An adaptive intrusion detection system takes proper decision to detect attacks properly resulting in high accuracy. The experimentation on proposed system which combines four approaches indicates enhanced performance. Keywords: Intrusion detection, adaptability, machine learning, ensemble
