The cornerstone of Windows 2000 security is Active Directory．Its support for granular access control，inheritance，and delegation of administrative task gives you the flexibility to secure resources without compromising your network’s purpose[7]．Fine-granted access control is not offered in NT 3．x or 4．0．This often torces you to assign permissions that give either too little or too much control[8]．Although Active Directory should be a significant piece of Windows 2000 security strategy，it can not deliver complete enterprise security by itself．