Analysis and Detection of Covert Information Transfers in MLS Network

Regarding the issue of network covert channels hidden in overt sources with fixed probability distribution,two detection methods are proposed.One is an improved attribute shift test and the other is a modified Pearson chi-square test.In attribute shift test we use k warnings instead of one warning to indicate detection.In chi-square test we incorporate adjacent probability values.The two methods improve detection accuracy in different degrees.Advantages of the detection methods are verified by experiments.