HTTP flood attacks have proven to be a long time challenge to internet web service. Various approaches have been devised to detect and mitigate against http flood attack, however, it is not always possible for a router on the adversary (i.e the victim path) to detect an attack in progress. Also most of the approaches only detects the presence of an attack. This research presented Enhanced Request threshold based collaborative detection and mitigation model to detect and mitigate against http flood attacks in progress irrespective of the path and the position of the adversary. Hence, this system will help to reduce HTTP flood attacks to a level that will ensure uninterrupted services to legitimate users. The res- ults gotten from the approach shows that an improvement of utilization performance of 64.33% against the scenario without Request threshold based scheme is recorded. This implies that Request threshold based detection and mitigation model provides 14.33% increment in cpu performance of web server under http flood attack against other ap- proaches such as the rate based detection and mitigation scheme. The research provides an algorithm for mitigating against http flood.