Log audits are the technical means to retrospectively reconstruct and analyze system activities for determining if the system is executed in accordance with the rules. This approach to compliance is referred to as compliance by detection. In the case of privacy adherence validation (or) privacy audits, the rules for compliance are less well defined and more contextual than in the case of traditional security audit. The aim of the paper is to understand the aims, techniques and challenges for realizing privacy compliance by detection. Using systematic literature review as the research tool we described the state-of-art privacy auditing approaches through taxonomies. We present two taxonomies, (i) classified in terms of auditing techniques and (ii) classified in terms of audit objectives. Following the observation gained from the state-of-the art we discuss challenges and suggest guidelines for utilizing log-based automated privacy audits.