To say firewall, Many Websites have taken down every day. Phishing websites and all others make the same effort to steal user information. You can block the whole country or the continent-wide, but they can still accessible through other ways.
How Internet Works
The definition of the Internet is the global system of interconnected computers which can communicate between networks and devices.
That means you can go by sea when you stuck in the land. The path will be long, but you can still reach there. When you connect to the Internet via Wi-Fi or Ethernet, You will have access to the Internet plus the Internet will have access to your computer too, vice versa. Your request via standard ports and get a response to non-standard ports.
A firewall is a kind of hardware or software which prevents users from accessing unwanted services or ports. They can drop or even break the connection that they do not want to.
However, a firewall cannot protect you from the attacks in full. You cannot block the whole word because you need them to visit your website.
Lock the gate fully or open and scan every entry
Imagine your website is a city, and the firewalls are the gates. You cannot lock-down the city by closing gates. You have to open some gates for visitors. When visitors arrive, you have to make sure that each of them is good or bad. When a visitor is trying to visit restricted sites, such as government offices or public safes, we need to stop him/her from visiting such areas. Otherwise, He/She may make an attack and costs you a city.
Can we secure the city?
Covid-19 is the best scenario for locking the city for fighting our unwanted guest. We secure the whole country, but we still can't win. Now, many lead to herds immunity.
How can we secure our people when the city opens?
We should have three layers of security named the restricted zone, private zone and public zone. The visitors can stay only in the latest ones. The citizens can stay in the middle ones, and the governments can only access all. It can vary on the architecture of your city.
As final, you cannot let visitors and citizens do strange things. You have to monitor every single point as a government. Sometimes, Citizens are worst than visitors. If you want to know, let's get an example of Troy.