The matrix of business and other transaction systems over the Internet makes computer security a critical issue in day-to-day activities. In recent times, various approaches ranging from rule-based, expert system to data mining have been subjected to extensive research in handling security breaches on computer networks. Immune System (IS) presents a protection against the possibility of malfunctioning and failure of individual host cells. In mammals it keeps the organisms free of pathogens which are unfriendly foreign organisms, cells, or molecules. Two approaches to change detection which are based on the generation of T-cells were examined.