Firewall

A firewall is a capability to limit network traffic between networks and/or information systems. This is a hardware/software device or a software program that limits network traffic according to a set of rules of what access is and is not allowed or authorized. This acts as a defense system against various threats against your computer or device.  
Firewalls also provide the ability to perform an important network security measure known as Network Segmentation. Network segmentation helps limit the spread of malware and viruses or even hacking intruders because the internal trusted network is no longer flat and open.  You need to be a member of the Finance team to be on the finance segment of the network.
Next generation firewalls may have advanced security capabilities such as Intrusion Detection and Prevention services which can be valuable, the ability to content filter, and some even provide SPAM Email filtering although a purpose built solution is still advisable.

Source: CNSSI 4009

Related TermsIntrusion DetectionIntrusion PreventionNetwork Segmentation

What should you do as a SMB?

As an SMB, it is important that you have a firewall in place for all Internet connected locations. A firewall is minimum essential security solution that prevents attackers from from breaching your systems and network. Just as important as having a firewall is enabling the many security features they contain to protect your infrastructure.

Network segmentation is also an important capability that should be leveraged with a firewall to create unique and distinct networks based upon work function in your internal network to limit the spread of malware or hackers who might breach one area but not all areas of your network.

Firewalls are commonly deployed in SMB’s with Wireless Network capabilities that allow you to physically and logically segregate guest WiFi networks from trusted WiFi networks.  Make sure you tie your Trusted WiFi network into your Active Directory user accounts (using Radius) instead of a static password.  This eliminates a common risk of terminated employees sitting on your trusted WiFI network in the Parking lot to siphon off sensitive data or cause additional harm to your company. 

Additional Reading:

What is a Firewall and How does it Work?

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