Abstract: In the strong interference background and low signal-to-noise,the accurate detection of network intrusion potential signal is the key of network security.The traditional Hilbert-Huang transform (HHT) intrusion signal detection algorithm has boundary control error resulted from envelope distortion,and spectrum leakage is occurred which leads the bad detection performance .An improved detection algorithm was proposed based on the time-frequency distribution feature and offset hierarchical control network HHT matching.The network potential intrusion mathematical evolution model is constructed,and the complex signals are decomposed into IMF single frequency signal.The intrusion detection system state transfer equation is obtained.The discrete analytical processing of the intrusion signal is taken based on Hilbert transform,and the signal model is obtained.The intrusion signal is decomposed with empirical mode,and the IMF component is analyzed by Hilbert spectrum.The HHT frequency shift is adjusted by hierarchical control mechanism,and residual projection and intrusion signal Hilbert marginal spectrum are matched.The envelope distortion is reduced,and the spectral leakage is suppressed.The accurate detection and parameter estimation of intrusion signal are achieved.Experiments show that this algorithm has strong anti-interference performance in intrusion signal detection,which can detect intrusion signal with low SNR effectively,and the performance of detection is improved.

Key words: Network intrusion,Detection algorithm,Hierarchical control