New trends in IT industry impose increasingly requirements on openness and interoperability via networks to enterprise software systems. As a consequence, more and more legacy applications are made available via interfaces more openly through mobile and insecure networks, thereby inducing security risks the initial designs have never had to account for. In this paper, we show how a highly automatable black-box method called fuzzing for testing security can be integrated into testing processes to increase interfaces of legacy application in terms of security profiles.