The benefits of cloud computing have attracted many organizations to migrate their IT infrastructures into the cloud. In an infrastructure as a service (IaaS) model, the cloud service provider offers services to multiple consumers using shared physical hardware resources. However, by sharing a cloud environment with other consumers, organizations may also share security risks with their cotenants. Distributed denial of service (DDoS) attacks are considered one of the major security threats in cloud computing. Without a proper defense mechanism, an attack against one tenant can also affect the availability of cotenants. This work uses a game-theoretic approach to analyze the interactions between various entities when the cloud is under attack. The resulting Nash equilibrium shows that collateral damage to cotenants is unlikely if the cloud service provider is unbiased and chooses a rational strategy, but the Nash equilibrium can change when the cloud service provider does not treat cloud consumers equally. The cloud service provider's bias can influence its strategy selection and create a situation where untargeted users suffer unnecessary collateral damage from DDoS attacks.