In pervasive computing systems, a higher number of interactions will be mediated by computers, amplifying the menace to privacy. Privacy protection in pervasive environments is still a big issue, despite the growing number of works on this subject as evidenced by this survey. In this paper, we propose a taxonomy for privacy invasion attacks, classify existing privacy enhancing technologies according to the protection provided for those attacks, and introduce a service-oriented privacy-enhanced architecture for pervasive computing.