What is a Firewall? And different types of firewalls.

A firewall is a system that is designed to prevent unauthorized access from entering a private network. A firewall blocks unwanted traffic and permits wanted traffic. Firewall is purpose is to create a barrier between private network and the public internet. A firewall is especially important to large organization.

• Firewall does a stateful Inspection
• Firewall maintain a list that which are allowed and which are not allowed.
• It works on (ACL)Access Control List . 

These firewall rules can be based on:-

• IP addresses
• Domain names
• Protocols
• Programs
• Ports

There are different types of firewalls:-

• Host-based firewall:- Software firewall that is installed on a computer protects that computer only 
• Packet filtering firewall:- It checks the source IP and destination IP but it does not check the payload what matter it contains.
• Application/Proxy firewall:-Proxy firewall does not let the internet know which computer actually wants to visit the website.
• Hybrid firewall:- Which combines both packet filtering firewall and application firewall in a series manner.
• Network based firewall:- It comes with combination of both hardware and software. And it protects entire organization