A firewall is a security mechanism that filters out the bad traffic that tries to access your private network. Like a metal detector installed at secure entrance points in buildings, a firewall is a virtual tool that scans data packets before they enter your company’s network. It checks these data packets against a set of predefined rules.
Like any other technology, the firewall has been updated with advanced security protocols that extend its usability beyond network protection.
The first firewall, a packet filter, was introduced in 1988, during the early internet days when computer geeks noticed that their systems were compromised. Today, we have grown so familiar with this network protection mechanism that no network security conversion is complete without mentioning the firewall.
Firewalls are classified into four types, each following a unique approach to keep your network, database, and employees safe. Your network might need more than one type of firewall for optimal performance. Keep reading to explore different types of firewalls, how they operate, and which is the best fit for your organization.
Software and Hardware Firewalls
Technically, you can use software, hardware, or a combination of these firewalls to ensure maximum network protection.
A hardware firewall is installed on your company’s router. It covers all the devices connected to this router. Before the data packets enter or leave your network, the hardware firewall scans them thoroughly. It checks the source address, a destination address, content type, and other factors to determine if the data packets are safe.
Physical firewalls are designed for organizations with many devices connected to the same network. They block malicious traffic trying to enter your company’s private network, but they aren’t reliable for offering protection against internal attacks.
Once the data packets access your company’s intranet, they are further checked by the software firewalls installed on each computer or internet device. This offers better security from insider threats.
Suppose you want an application not to enter a few selected devices. Your hardware firewall will restrict this application for all devices, whereas the software firewall will restrict them only to the devices that are configured to block these apps.
A software firewall can be configured depending on the level of security you need for different internet devices.
According to a 2019 report, 40% of companies have installed on-premise firewall protection, while 60% have the combination, which includes firewalls installed partially on the cloud.
Types of Firewalls and How they Work
1. Packet Filtering Firewall
The most popular and oldest firewall protection is packet filtering. These firewall programs match the data packets received against the predefined security criteria and either block or accept external requests.
When scanning data packets, the packet filtering firewall verifies the source IP, destination address, IP address, and packet type. Data packets that are identified as malicious or harmful in any way are dropped right there.
Packet filtering is fast, cheap, and easy to implement. A single system can cover the entire network without affecting the end-user experience or slowing down the network. Unfortunately, it can’t detect bigger or more serious threats beforehand. That’s because packet filtering is limited to the port numbers and IP addresses.
For small and budget companies, packet filtering provides basic security against known threats. You can use it as a standalone product or combine it with other firewalls for advanced protection.
2. Circuit-Level Gateways
Circuit-level gateways verify the TCP handshakes. When a connection between a local device and a remote host is initiated, this firewall mechanism checks the authenticity of the connection.
Simply put, circuit-level gateways ensure that the remote host that you are connecting your devices to is legitimate and secure. These are similar to packet filtering in that they scan the remote hosts thoroughly before establishing a connection. They are inexpensive and use minimal resources.
However, the downside is they don’t scan the data packets. This means that malicious data packets infected with viruses or malware can pass through the circuit-level gateways if they have a secure TCP handshake.
3. Stateful Inspection Firewall
For broader coverage and the best protection, you should consider a stateful inspection firewall. It checks the data packets and the TCP. The firewall blocks data packets that don’t come from an established and authentic network session.
The stateful inspection firewall offers robust security, as they cover IP addresses, port information, and payloads. However, they can take a toll on your network performance. As a result, the traffic might slow down and can be at risk of Distributed Denial of Service attacks.
4. Application-Level Gateways
Application-level gateways cover all interactions taking place between an external network and the network protected by this firewall. This includes the IP addresses, port, TCP handshake, and the content before it can access your system.
The program offers exceptional security controls. For example, it can allow an external user to access a website but limit the pages they can visit. It also maintains user anonymity.
Application-level gateways are called proxy firewalls. Once they are installed, all your connections will be established through proxy. It scans the data packets and content type based on your pre-defined security criteria.
Protection-wise, this is your ultimate choice. Not only it protects your data from getting leaked outside, but the firewall blocks the malicious sites that can be harmful to your network.
It isn’t suitable for all network protocols, though. Proxy firewalls can delay communications and are difficult to manage because of the resources they use for operation.
No security mechanism can accurately predict which type of content poses a threat to your company’s network. However, the updated security technology records the risk pattern, based on which it determines whether the data packets are benign or malicious.
Each type of firewall aims to scan the data before letting it in. If the security protocols signal previous attacks from a specific data packet requesting access to your system, it gets blocked immediately.