Collaboration technologies are making it easier for organizations and knowledge workers to collaborate across organizational boundaries. However, it is necessary for organizations to monitor, regulate and build appropriate security mechanisms in collaboration systems to prevent loss of strategic knowledge and competitive advantage. In this paper, we present a risk assessment framework that can help organizations identify valuable knowledge assets that can be exposed through collaboration technologies, and help prioritize security strategies that can be used to secure the collaboration systems to prevent the loss of valuable knowledge assets. We present an illustrative case to demonstrate the feasibility of the framework, and discuss issues for future research.