Along with the emergence of Web 2.0 there is a need for accessing information in a continues and secure way using whatever device available for doing so. In such a context, access to information resources must be done in a secure and robust way through services that come up as a new paradigm for programming and organizing operations. This paper presents an approach for retrieving critical and non critical data with different security constraints by coordinating services. Thanks to contracts describing the logic of a services based application running in a dynamic environment, it is possible to associate a personalized secure behavior in an orthogonal way. Contracts ensure, for example, integrity and authentication of services at execution time in the presence of exceptions and make applications aware of their execution context.