Cyber attacks have become ubiquitous and in order to face current threats it is important to understand them. Studying attacks in a real environment however, is not viable and therefore it is necessary to find other methods how to examine the nature of attacks. Gaining detailed knowledge about them facilitates designing of new detection methods as well as understanding their impact. In this paper we present a testbed framework to simulate attacks that enables to study a wide range of security scenarios. The framework provides a notion of real-world arrangements, yet it retains full control over all the activities performed within the simulated infrastructures. Utilizing the sandbox environment, it is possible to simulate various security attacks and evaluate their impacts on real infrastructures. The design of the framework benefits from IaaS clouds. Therefore its deployment does not require dedicated facilities and the testbed can be deployed over miscellaneous contemporary clouds. The viability of the testbed has been verified by a simulation of particular DDoS attack.