Protecting Scientific Workflows in Clouds with an Intrusion Tolerant System

With the development of cloud computing technology, more and more scientific workflows are delivered to cloud platforms to complete. However, there are many threats in clouds due to the multi-tenant coexistence. In order to protect scientific workflows in clouds, the authors propose an intrusion tolerant scientific workflow system. In this system, the task executors containing multiple virtual machines are used for workflow sub-task execution to enhance reliability. Then lagged decision mechanism is presented to ensure uninterrupted workflow execution while checking the intermediate data, and assessing the confidence of these data. Inspired by moving target defence, they propose a dynamic task scheduling strategy based on resource circulation to periodically generate and recycle task executors, keeping the clean state of the workflow execution environment. Furthermore, temporary workflow intermediate data backup mechanism is presented, the stored intermediate data can be used for the re-execution of workflow sub-tasks with low confidence. Experiments are conducted in both the actual test environment based on OpenStack and the simulated test environment based on WorkflowSim toolkit. Experimental results demonstrate that the proposed system can effectively enhance intrusion tolerance of scientific workflows.