Protection against trojan horses by source code analysis

Abstract

The technology of security in computer networks has far-reaching implications. In this paper, assuming a UNIX network system, which is the most popular currently, we enumerate the threats against security and classify the problems. Among the problems so defined, we consider particularly the Trojan horse problem, which is important when a program is received from the outside; and we propose a method of protection against Trojan horses. In the proposed protection method, objects which have been modified by the source program are extracted and are compared with a previously prepared list (the condition list) of objects which should not have been modified. In this method, verification of the security of the program needs to be done only at the time of its installation, so there is no loss in efficiency of performance at run time. Also, we can prevent security violations which cannot be regulated by controlling access and flow. In the proposed method, the major problem is determining the extent to which altered objects can be detected. In this regard, we perform soine experiments on the free software X11R4 and TeX. Finally, based on the results of the experiments, we evaluate the proposed protection method on the security of programs imported from the outside.