What is multifactor authentication security and explain: when you sign into your online accounts a process we call 'authentication', you're proving to the service that you are who you say you are. Traditionally that's been done with a username and a password. unfortunately, that's not a very good way to do it, usernames are often easy to discover, since password can be hard to remember, people tend to pick simple once, or use the same password at many different sites. That's why almost all online service banks, social media, shopping and yes, microsoft365 too have added a way for your accounts to be more secure, you may hear it called 'Two-step verification' or 'multifactor authentication' but the good once all operate off the same principle. when you sign into the account for the first time on a new device or app (like a web browser) you need more than just the username and password. You need a second thing , what we call a second 'factor' to prove who you are.