What is the Authenticator?
The RuneScape Authenticator provides an extra layer of security for your RuneScape account. In addition to using your username and password when you login, you will also use a code generated by an application running on your device.
As long as your registered email address is secure, with the RuneScape Authenticator enabled, no one will be able to access your account unless they have your username, password and the code generated by your device.
Turn on the Authenticator
Check if the Authenticator is active on your account, if not turn it on: