  Today's cloud apps are built from many diverse services that are managed by
different parties. At the same time, these parties, which consume and/or
provide services, continue to rely on arcane static security and entitlements
models. In this paper, we introduce Seit, an inter-tenant framework that
manages the interactions between cloud services. Seit is a software-defined
reputation-based framework. It consists of two primary components: (1) a set of
integration and query interfaces that can be easily integrated into cloud and
service providers' management stacks, and (2) a controller that maintains
reputation information using a mechanism that is adaptive to the highly dynamic
environment of the cloud. We have fully implemented Seit, and integrated it
into an SDN controller, a load balancer, a cloud service broker, an intrusion
detection system, and a monitoring framework. We evaluate the efficacy of Seit
using both an analytical model and a Mininet-based emulated environment. Our
analytical model validate the isolation and stability properties of Seit. Using
our emulated environment, we show that Seit can provide improved security by
isolating malicious tenants, reduced costs by adapting the infrastructure
without compromising security, and increased revenues for high quality service
providers by enabling reputation to impact discovery.
