This paper explores a novel danger theory based model to aware the situation for TCP SYN flooding attacks. Within in the presented model, the TCP SYN flooding attacks are looked as dangerous exogenous patterns, and induce danger signals to aware the situation of host computers, which is realized by hosted-based artificial immune detectors. After summarizing the danger theory, the model framework, correlative concepts, TCP SYN flooding attack detection, danger signal computation and attack situation awareness methods are described. Following that, the interrelated techniques are compared. Theoretical analysis results show that the proposed model is valid. Thus, it provides a good solution to computer network security.