The paper begins with an introduction that describes the concept and importance of power system security. The mathematical model is built depending on both the linear load flow technique and the sensitivity factors for line and generation outages. The algorithm has been designed so that a power system of arbitrary bus number and voltage levels can be studied. This algorithm has been programmed in Borland Pascal in interactive mode, and the developed program has been tested on several test systems. The Program has been used for security assessment of a part of the Syrian 230 kV network. The obtained results have shown the validity and effectiveness of the program in spite of using linear models. It is worth saying that the developed program is the first one for security assessment in Syria so far.