Current event processing systems lack methods to preserve privacy constraints of incoming event streams in a chain of subsequently applied stream operations. This is a problem in large-scale distributed applications like a logistic chain where event processing operators may be spread over multiple security domains. An adversary can infer from legally received outgoing event streams confidential input streams of the event processing system. This paper presents a finegrained access management for complex event processing. Each incoming event stream can be protected by the specification of an access policy and is enforced by algorithms for access consolidation. The utility of the event processing system is increased by providing and computing in a scalable manner a measure for the obfuscation of event streams. An obfuscation threshold as part of the access policy allows to ignore access requirements and deliver events which have achieved a sufficient high obfuscation level.