Web services interact with sensitive data such as credit card numbers, it is very important for web services to be able to ensure security. To this end, they include a wide range of technologies and specifications that when combined can provide integrity, confidentiality and authentication. This paper discusses the basic concepts of WS-Security and the related technologies. The complexity caused by the overhead to the overall process of web services transactions is analysed and evaluated. Extended experiments have been conducted in order to measure and compare the security mechanisms.