While it provides the unprecedented processing power to solve many large scale computational problems, GRID, if abused, has the potential to easily be used to launch (for instance, denial-of-service) attacks to other computer systems. This paper introduces a methodology to prevent GRID infrastructure from succumbing to such activities. Our system is designed to detect, classify, and control GRID-abuse attacks. The current implementation of our system uses system calls as raw features, while the chi-square statistical method is used for attack detection, and fisher linear discriminant analysis is used for attack classification. The performance evaluation shows our system can achieve a high detection rate (over 92%) with very low false alarm rate (virtually zero), and small detection delay (about 10 seconds). For the detected attacks, our system classifies them with average accuracy over 82%.