ReqView sends no project data to the internet. It persists all data about open projects in the secure local application storage, which is typically located in your home folder, for instance in C:\Users\<user name>\AppData\Roaming\ReqView folder on Windows.
If you save a project on your local or shared network drive as a Project File or a Project Folder then it is stored in open file data format based on JSON. You should protect these files from unauthorized access by file access rights on your computer or a file server.