  Dependability is an important characteristic that a trustworthy computer
system should have. It is a measure of Availability, Reliability,
Maintainability, Safety and Security. The focus of our research is on security
of web services. Web services enable the composition of independent services
with complementary functionalities to produce value-added services, which
allows organizations to implement their core business only and outsource other
service components over the Internet, either pre-selected or on-the-fly. The
selected third party web services may have security vulnerabilities. Vulnerable
web services are of limited practical use. We propose to use an
intrusion-tolerant composite web service for each functionality that should be
fulfilled by a third party web service. The third party services employed in
this approach should be selected based on their security vulnerabilities in
addition to their performance. The security vulnerabilities of the third party
services are assessed using a penetration testing tool. In this paper we
present our preliminary research work.
