Different Types of Firewalls Explained – Which one To Use?
Firewalls are an essential component of network security in the client-server model. These systems ensure that both incoming and outgoing traffic is secure, but they are susceptible to social engineering attacks, such as when someone steals a password to commit CEO fraud, insider threats, when someone within the network intentionally alters firewall settings, or human errors, such as an employee forgetting to activate the firewall or ignoring update notifications.
How exactly does a firewall work? What is its functioning?
A firewall acts as a barrier between a network and external sources by being placed in-line. This creates check points where all data packets entering and exiting the network are examined. A packet contains the payload (the actual content) and a header (information about the data, such as who sent it and to whom).
By preset rules, firewalls examine packets to differentiate between benign and malicious traffic. These rulesets govern how the firewall scrutinizes the following:
- Source and destination IP addresses
- Payload content
- Packet protocols (e.g., whether the connection uses a TCP/IP protocol)
- App protocols (HTTP, Telnet, FTP, DNS, SSH, etc.)
- Data patterns that indicate specific cyberattacks
The firewall blocks all packets that violate the rules and forwards secure packets to their intended recipients. There are two options when a firewall stops incoming traffic from entering a network:
- Discard the request silently
- Send an error response to the sender
Both options prevent dangerous traffic from entering the network. It is preferable to drop requests silently to reduce the amount of information released if a potential hacker is attempting to test the firewall for vulnerabilities.
Firewalls are used to keep networks safe from external traffic sources, build walls around internal subnetworks, and set up traffic scanning on a single device. They are a fundamental component of network security in the client-server model. Despite protecting incoming and outgoing traffic, firewalls are susceptible to social engineering attacks, insider threats, and human mistakes.
What are the different types of firewalls? Which one should I use?
You can define types of firewalls in two ways, based on delivery method and based on operation method.
Based on Delivery Method
- Software Firewalls
- Hardware Firewalls
- Cloud-Based Firewalls
Based on Operation Method
- Packet-Filtering Firewalls
- Circuit-Level Gateways
- Stateful Inspection Firewalls
- Proxy Firewalls
- Next-Generation Firewalls
- Software Firewalls:
Software firewalls, also known as host firewalls, are installed directly on a single device and provide protection for that specific device. To safeguard multiple devices, administrators must install a software firewall on each one. However, using a software firewall can consume system resources, including CPU and RAM, which may be unsuitable for certain use cases.
- Hardware Firewalls:
Hardware firewalls, also known as appliance firewalls, are separate pieces of hardware that filter incoming and outgoing network traffic. These devices have their own resources and do not rely on the resources of the host devices, unlike software firewalls. For smaller businesses, a hardware firewall may be excessive, and they may prefer to use per-host software firewalls. Hardware firewalls are an ideal choice for larger organizations that have several subnetworks containing multiple computers.
- Cloud-Based Firewalls:
Cloud-based firewalls, also known as Firewall-as-a-Service, are provided by many vendors and are delivered on-demand over the internet. These services can be run as Infrastructure-as-a-Service or Platform-as-a-Service. An MSP manages cloud-based firewalls, making them an excellent option for highly distributed businesses, teams with gaps in security resources, and companies without in-house expertise. Cloud firewalls can be set up either on a per-host basis or for perimeter security, much like hardware-based solutions.
- Packet-Filtering Firewalls:
Packet-filtering firewalls act as a checkpoint at the network layer, comparing each packet’s header info to a set of pre-established criteria. They only examine surface-level details, such as destination and origination IP addresses, packet type, port number, and network protocols, without analyzing the packet’s payload. Packet-filtering firewalls are a good choice for small organizations that require a basic level of security against well-established threats.
- Circuit-Level Gateways:
Circuit-level gateways operate at the session OSI layer and monitor TCP handshakes between local and remote hosts. They quickly approve or deny traffic without consuming many resources. However, these systems do not inspect packets, so even malware-infected requests may gain access if there is a proper TCP handshake.
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- Stateful Inspection Firewalls:
Stateful inspection firewalls, also known as dynamic packet-filtering firewalls, monitor incoming and outgoing packets at the network and transport layers. This type of firewall combines packet inspection and TCP handshake verification. They maintain a table database that tracks all open connections and enables the system to check existing traffic streams. Stateful inspection firewalls are an excellent choice for businesses that require more sophisticated security measures.
- Proxy Firewalls:
Proxy firewalls serve as intermediaries between internal and external systems, protecting a network by masking client requests before sending them to the host. They operate at the app layer, the highest level of the OSI model, and have deep packet inspection capabilities, checking both payloads and headers of incoming traffic. Proxy firewalls are the go-to option for businesses trying to secure a web application from malicious users or when a use case requires network anonymity.
- Next-Generation Firewalls (NGFWs):
Next-generation firewalls combine several functions of other firewalls, including deep packet inspection, TCP handshake checks, and surface-level packet inspection. They also include additional network security measures such as intrusion detection and prevention, malware scanning and filtering, advanced threat intelligence, antivirus programs, network address translation, quality of service features, and secure shell inspection. Next-gen firewalls are commonly used in heavily regulated industries such as healthcare or finance. Companies that must adhere to HIPAA and PCI typically adopt these firewalls.
Choosing the Right Type of Firewall
When it comes to choosing the right type of firewall for your business, you must consider what kind of network you are protecting, how valuable your assets are, if you use mission-critical applications, how much budget you have allocated to cybersecurity, what kind of traffic your firewall will face, whether the load be consistent, if you need firewall on each device, what kind of traffic inspection you need, and how much latency you can afford. A professional in this field can help guide your decision.
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