FAQ - Multifactor-Authentication (MFA)

FAQ - Multifactor-Authentication (MFA)

Which services are protected by MFA?
Which tokens are usable?
Which hardware tokens can be used?
How do I obtain a hardware token?
Why are there different hardware tokens?
How do I set a token as the default?
Why am I asked twice for a second factor in some services?
My tokens are not working. What do I do?