Beyond accountability: using obligations to reduce risk exposure and deter insider attacks

Recently, the importance of including obligations as part of access control systems for privilege management, for example, in healthcare information systems, has been well recognized. In an access control system, an a posteriori obligation states which actions need to be performed by a user after he has accessed a resource. There is no guarantee that a user will fulfill a posteriori obligations. Not fulfilling these obligations may incur financial loss, or loss of goodwill and productivity to the organization. In this paper, we propose a trust-and-obligation based framework that reduces the risk exposure of an organization associated with a posteriori obligations. We propose a methodology to assign trust values to users to indicate how trustworthy they are with regards to fulfilling their obligations. When access requests that trigger a posteriori obligations are evaluated, the requesting users' trust values and the criticality of the associated obligations are used. Our framework detects and mitigates insider attacks and unintentional damages that may result from violating a posteriori obligations. Our framework also provides mechanisms to determine misconfigurations of obligation policies. We evaluate our framework through simulations and demonstrate its effectiveness.