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