Samsung has anti virus built in. Thats basic protection which I assume most phones have anyway.
But it also has knox security system, which protects phone at each layer. Fun stuff.
On top of that, there is maximum power saving mode which acts as security as well because it shuts down all apps except few selected ones. If you enable "limit apps" option, all apps except the ones you select are shut down until you allow them.
But there is even much more. If you enable "Developer mode" in your phone, there are two more security options there. One is to not allow any backround processes, called "Limit backround processes". The other is to destroy any activity as soon as user leaves it.
And finally, cleaning RAM basically shuts down everything thats left.
These options not only significantly speed up phone by shutting down activities and freeing up resources for apps you actually use, but they act as such strong security that hacking a phone set up in this way is actually impossible.
Additional security from hacking comes from the fact that you can disconnect from internet when you dont use internet, making any hack attempts much more difficult.
Further, it is not possible to install anything on the phone without user's permission, due to "stop unknown apps" system which doesnt let unchecked apps install.
