Date Added: Feb 2012
The network information system based on Multi-Level Security Strategy (MLSS) is adopted by many organizations, as it reflects features of mandatory access control. Meanwhile, the network has also attracted a growing number of Trojan horses' attacks. Considering the relationship between defend ability and security levels, the paper discusses that the Trojan horses' attacks have a dependency on data path in the network and establishes three attacking probability models of single source node to single target node by single-path, single source node to single target node by multi-path and multi-source nodes to single target node by multi-path. Furthermore the paper describes the defend ability of the non-adjacent nodes with a new model.