Abstract: Grid computing is an emergent computing innovation which offers endless access to computing infrastructure across various organizations (academia and industry). Since this technology allows aggregation of various computer systems for usage by different users to run applications, the information stored on it which may be sensitive and private, remains vulnerable. According to related research on the attribute based access control for grid computing there is no adequate and appropriate security mechanism to authorize and authenticate users before accessing information on a grid system. The issue of security in grid technology has not been fully addressed even though it is a precondition for optimizing grid usability. In this paper therefore, we try to explore some of the main security attacks on a grid system and provide reasonable countermeasures to handle the situation. Finally, an architectural model to prevent any form of attacks explained is also presented.