Network firewalls are security devices used to prevent or restrict unauthorized access to private networks connected via the internet. The access to the network is based on some user-defined rules and any traffic that doesn’t obey these rules is filtered.
See a firewall as a gatekeeper whose job is to allow a certain set of people into a house. Say, those with red dresses. If your dress isn’t red, you’re out.
How do Firewalls Work?
Firewalls work by using one or a combination of the following methods to make sure that only authorized traffic flow in and out of a network.
1. Stateful inspection
The stateful firewall works by collecting significant attributes of the connection to a trusted database for the duration of the session. These attributes are collectively known as the state of the connection.
This information is then being compared to the copy relevant to that transfer in the database. If there is a positive match, the information is granted access. Otherwise, –– access denied.
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2. Stateless or packet filtering
Packet firewall examines every packet of information (little amount of data) that comes into the network and checks if it meets the criteria set by the user.
If it matches, the information is allowed through but if it doesn’t correlate, the information is flagged and denied access.
3. Application-layer Firewalls
This is usually a hardware appliance or software filter. It works by layering mechanisms on top of defined applications, such as defining rules for HTTP connections.
The rules are separately built for each application to help track and filter incoming attacks.
How many types of firewalls do we have?
There are two types of firewalls:
1. Hardware Firewalls
Hardware Firewalls are very important in any security system or network configuration. They are usually built-in components of a router or other networking device. Hardware firewalls use packet filtering to observe the header of a packet and after comparing it to a set of pre-defined rules, they decide to accept or drop it.
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2. Software Firewalls
Software filtering is the most common for home users. They may come as different software or come as standalone software. They use different techniques to prevent malicious information from entering into your server.
I hope you understand what network firewall is all about and how they work. Share your views about network firewalls with us.
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