XFI Advanced Secuirty

Tatyana1 -- You can choose to have the feature enabled or disabled.  You can read more about xFi Advanced Security and decide if it would benefit you here -- 
https://www.xfinity.com/support/articles/getting-started-with-xfinity-xfi-advanced-security
https://www.xfinity.com/support/articles/xfinity-xfi-faqs

Tatyana1 -- Thank you for reaching out.  The xFi Advanced Security feature is now included with your Gateway and is rolling out to customers with compatible Gateways over the next few weeks.  

When logging into xFi recently, you should have seen a What's New screen with some information about this.  

Thank you for posting a link but I'm not technically savyy enough to decide if its for me or not.  I want to be protected but at the same time Im afraid that the system might start blocking things or act extremely restrictive. The default firwall setting in admin tool is low security, so may be too much security is not good. If you can shine more light that would be great.

You can always chose to enable the feature and see how it works for you. 
With the feature enabled, whenever a threat is detected, it’s automatically blocked and you are notified in xFi and given tips on how to resolve.  You can also choose to enable push notifications for threats.  For certain threat types, you can opt to allow access for a certain period of time.  (Keep in mind that by doing so, you may be putting your network at risk and making it vulnerable to malicious activity.)

 You retain the ability to enable and disable the feature yourself.  Here is another article with additional information about threat types and how to enable/disable the feature -- 
https://www.xfinity.com/support/articles/using-xfinity-xfi-advanced-security

The modem existed without it for a long time and everything was fine, so I don't see how this feature is gonna make anything better, I don't trust it.

Never Mind

Is protected browsing only available on one model?