On certain occasions once you log in to your Google account, you might be asked to provide your telephone or cell phone number. This is a legitimate request from Google.
Why does Google ask for this?
It is part of their Login Challenge for suspicious sign-ins. Your phone number (and in particular, your cell phone number) is a piece of information that Google can use to verify who you are. They won't share it with anyone else.
In an effort to protect you from account spammers and abuse, Google will sometimes ask you to prove you're not a robot before you are able to sign in to your account. Having this additional confirmation via phone is an effective way to keep spammers from abusing Google's systems.
For example, if Google detects a suspicious login or if someone has hijacked your account, if Google has your phone number they can send a text message, call you, or use your cell phone number as a way to notify you about suspicious activity. This drastically reduces the chances of an unauthorized person accessing your account.
Do I have to give Google my phone number?
As of today, it's not required that you add a phone number to your UCSC Google account. We've heard through the grapevine that Google will soon begin requiring this information, but we don't know exactly when this will be implemented.
Even if Google requires it, there’s nothing preventing you from putting in a bogus phone number. It doesn’t serve you very well, because if you need to recover your account or if Google needs to verify who you are, you won’t have that option. It's important that you use a real phone number so Google can reach you.
More information is available at: https://support.google.com/a/answer/6002699?hl=en
Posted by: Lisa Bono