When you are away from your home and connect to the MiOS system in your home through the mios.com portal, it uses a secure web page, with the same type of security used for online banking.  You can see this by the https:// in the address bar of your browser.

When you are inside your home, on your local home network, normally you can connect directly to your MiOS system without going through the secure mios.com portal, and without supplying a password.  You can this because the address bar in your browser has http:// and not https://.  This makes it convenient to access MiOS from within the home since you don't need a username and password, but it also means that anybody who has physical access to your home network, such as access to your computer, can access the MiOS system.  If you have a wi-fi access point that is unsecured, and therefore allows passersby to hop onto your home network, they can also control your MiOS system.

To prevent this, you can require your MiOS system require a password from within the home, as well as outside the home.  Simply login to your mios.com account, click the 'Settings' link next to the MiOS system, and check the box 'Require local http authentication'.  This means that your MiOS system will require you to enter your mios.com username and password to access it from within the home as well.  With this setting, you may have to enter your username and password more often, or be asked for it twice.  Local http authentication is the same as what's used by any other network devices you may have on your home network, like access points, cameras and so on.  Note that this 'local http authentication' is not as secure as the https security that is used on mios.com.