This document summarizes and compares various techniques for clustering and protecting categorical data to preserve privacy. It discusses subtractive clustering, robust hierarchical clustering, decision tree clustering, outlier detection methods like statistical, depth-based, distance-based and density-based techniques. It also covers protection algorithms such as L-diversity and an evolutionary optimization approach. Tables are provided to compare the benefits and drawbacks of different clustering, outlier detection and protection algorithms for categorical data privacy. The document concludes that clustering is useful for categorical data privacy but challenges remain in improving utility and security.