UC Berkeley uses CalNet 2-Step verification to better protect identities and accounts behind two-factor authentication.
The first step is your CalNet passphrase. Make sure that your passphrase is a strong one.
The secondary step is a verification click or code, which confirms your identity and protects your account in the event that your passphrase is stolen or hacked.
CalNet 2-Step pops up following CAS login. You can choose to verify by: (a.) push notification, (b.) answering a call, or (c.) entering a passcode. Typically, Campus users choose to click on the push notification, which is easily received on smartphones, through the Duo Security app. You can download the Duo app through the Android/Google Play Store or the Apple/App Store.