Distributed denial of service is major security threat that has been increasing today. If network size increases, the security threats problems becomes more severe. Therefore, intrusion prevention/detection becomes mandatory. The system differentiates the traffic coming from the authorized user and an intruder. The introduction of IPS aims at preventing the attack as far away from destination server. Denial of service can be of any form either pings of death, teardrop attack, smurf attack and clone attack. In existing system, these attacks can be overcome by using filter Firecol technique.