Hello, today, one of the most tools used for the network security is the Firewall. But are exactly firewalls and their the different types
Firewalls are the foundation of defense-in-depth network security strategy. They are designed to protect organizations from network-based attacks. They are filtering data packets that o through them.. They can be a standalone network device or software on a computer system,meaning network-based(hardware) or host-based (software)
Types of firewalls
Packet filtering firewall
1st generationand most basic type of firewall, the most unexpensive one.
How they works: They inspect all data packets that attempt to traverse it, and based on pre-defined rules , packets are either allowed or denied
These predefined rules are commonly called an Access Control List (ACL)
Now how this rules are setup , they base on common TCP/IP packet attributes (source and destination ip address , destination and source ports , ip protocol etc...)
Circuit-level Firewalls
They operate at the transport layer of the OSI model (Layer 4) and monitor TCP/IP sessions.
Instead of analyzing each individual packet, they monitorthe TCP handshake
Valid TCP sessions are allowed to pass, while invalid and terminated sessions are not
Hackers can alter the 3-way handshake process attempting to cause denial of service (Dos) attack
If the firewall believes an attack is occuring, it will block the traffic
Application-level firewalls
Also known as proxy servers, these firewalls operate at te Application layer of the OSI model (layer 7)
Specifically ,proxy servers can provide the folowing services:
Filter: Filters packets based on an application or service (FTP,SMTP,etc...)
Caching: Provoides caching services
Logging: Has the ability to log user activity for auditing purposes
Stateful Multilayer inspection Firewalls
Provide the functionality of packet filtering , circuit-level and application-level firewalls combined
Can filter traffic at the OSI model Network layer with ACLs
Can filter traffic at the OSI transport layer ny monitoring TCP sessions
Can also fiter traffic at the OSI application layer based on an application or servuce (FTP,DNS,HTTP,Etc...)
They are also the most expensive type of network Firewall
Thanks
