Update 2018
Starting with Adaxes version 2018.1 Web interface access is controlled in the Web interface configurator. For details, have a look at the following tutorial: https://www.adaxes.com/tutorials_WebInterfaceCustomization_AllowDenyAccessToTheWebInterface.htm.
Original
In the Web.config file that is located in the C:\Program Files\Softerra\Adaxes 2\Web Interface folder, specify the users you need in the <authorization> element:
<authorization>
<allow users="username1@domain.com,username2@domain.com" />
<deny users="*" />
</authorization>
At the moment it is possible to allow or deny specific users (not groups) to connect to Adaxes Web Interface. In the next version (2011.1) it will be also possible to specify groups.