You can only enable this feature if you are an Owner of a server and have Two Factor enabled on your own STORM account. Once this feature is enabled users with Two Factor switched off on their account will not be removed from that server but will not be able to access it until they switch on Two Factor. You can enable Two Factor on any STORM account by clicking Profile and then Security.
Two Factor is an extra layer of security when logging into STORM. STORM will require you to enter a 6 digit code along side your password. The 6 digit code changes every 60 seconds based on a HMAC based algorithm. You can use any HMAC based algorithm on STORM although we recommend either 1Password or the Google Authenticator available on iPhone or Android. If you regularly use the same computer you can tick for STORM to remember you so you do not have to enter the code each time.