In computing, the software elements like objects and components emphasize on reusability using design tools of abstraction and separation of concerns. Software architecture has appeared as an initial idea to develop huge, complicated and heterogeneous distributed systems successfully. Service Oriented Architecture (SOA) combines services together to make systems having a greater impact on the way software systems are developed. SOA addresses the need of standards-based, loosely connected, and distributed computing which is protocol independent. It is not easy to ensure the secure transaction of data, where the movement of data occurs through loosely connected services. A number of techniques have been proposed in the contemporary literature to guide the SOA implementation in distributed system. These techniques offer certain benefits, but pose some challenges alongside such as the use of meta-data as framework and standard, contract documents, security patterns and security adviser, etc. The objective of this research is to provide a comprehensive analysis of various approaches used to provide application level security to the web services in SOA. These approaches have been compared based on a number of parameters. In addition, we critically evaluate different security methods used in SOA. The study also discusses some future directions in this domain.