Which of the following are true about network$-$centric approach to security?

Network$-$centric approach to security deals with attacks in a reactive way.

Network$-$centric approach to security deals with attack proactively.

Network$-$centric approach to security is based primarily on finding and fixing known security problems after they've been exploited in fielded systems

Network$-$security approach to security usually tries to block malicious input.