I work for a large corporation that shall remain nameless, providing support for some of these systems. As BozemanMT said, they are generally heavily customized for each department and the CAD systems are in fact very dated for the most part. I primarily provide support for records management systems, which contain far more information about people and crimes than the CAD systems, which generally dump all their information into the records system.
The records system is much more up-to-date and using much more modern technology (the one I mainly handle is anyway, although I also support an old DOS-based one still in use by hundreds of client-agencies). The security of these systems is entirely up to the client agency; it's all about server security.
As for worries about misuse of the info on these systems, BozemanMT nailed it on the head. These things barely talk to each other. It's all we can do to keep the internal systems talking to each other, as the various pieces of software are often from differing vendors. And generally, the only info going to the feds from your local police is stripped-down statistics for Uniform Crime Reporting, or National Incident Based Reporting, depending on the state. The systems just aren't designed for sharing anything other than statistical details with anyone outside the agency.
