Mutation analysis is a fault based testing method used initially for code based software testing, and lately for specification based testing and validation as well. In this paper, the method is applied to SDL (Specification and Description Language) specifications. It is used to automate the process of conformance test generation and selection for telecommunications protocols. We present two algorithms for automatic test generation and selection. These provide the basis of the Test Selector tool developed at the Budapest University of Technology and Economics. We present the results of an empirical study using the tool.