A firewall is a device that allows multiple networks to communicate with one another according to a defined security policy. You can implement a firewall in either hardware or software form, or a combination of both. When there are different levels of trust among the different parts of network, a firewall can and should be used.
A common misconception about firewalls is that they are only necessary for large companies or financial corporations. In reality, every business that has a network should have a firewall, regardless of the size of your company.
Over half of all cyberattacks today are targeted at small businesses, because smaller businesses typically have a myopic view that cybercriminals will not target at them. Hence, they have lesser or rudimentary network security which in fact makes them the easiest prey. Also, cybercriminals are continually evolving their strategies and finding new, more sophisticated ways to penetrate through the network security, and steal your company’s most valuable asset – your data.
Thus, this is where the firewall earns its keep.
There are multiple ways to categorise traffic into “Permitted” and “Not Permitted” categories. For instance, we can configure your firewall on which types of traffic are permitted to access and which ones it should block. Each approach corresponds to a different firewall “layer”.
Categorise traffic according to IP addresses, port numbers and service protocols.
Categorise traffic according to which application or application service the traffic trying to reach, and the specific content of that traffic are.
Packet Filtering- to allow or block individual network packets depending on where they originated and which ports they want to talk to.
The application firewall accept traffic on that port in general, but block any traffic that contains a known vulnerability.
L3 make decisions based on a much more narrow set of variables (IPS and Ports) than L7 firewalls. On the other hand, and L7 firewall is able to look within the app layer, and make decisions about whether to allow a request based on what it contains, not just the port it’s trying to reach.
Thus, L7 is one firewall that provides significantly greater security, but this is a more computationally costly operation.