Security design, implementation and integration are specialties, too. Design the security into the project from the beginning. It's a whole lot cheaper than bringing in folks like me later on to fix your mistakes. We charge less for helping you do it right the first time. Security is integral to any quality information technology environment today.
Project management is about making all of the pieces work together.
Security is a piece. You beta-test your applications before deployment. If your project manager tells you the security is perfect and doesn't need testing, refer to the second item in this list. Test the system thoroughly using people who have expertise and who do not have an internal corporate political agenda. There is no magic here - just some common sense, a mild dose of humility and the acceptance that maybe, just maybe, you might overlook one tiny detail, misconfigure a device or make a mistake.