GeoWebCache requires authentication to perform certain operations, such as reconfiguration or seeding. By default WEB-INF\users.properties looks like this:
Change geowebcache to your desired username and secured to your password of choice. It is recommended that you use only ASCII characters.
Fine-grained control can be implemented using an external proxy or servlet filter, or within GeoWebCache by using a request filter. Advanced users who understand ACEGI may want to edit acegi-config.xml as well.