Firewalls protect your internal network from threats. They are an essential element of a cybersecurity strategy.
Firewall types vary in structure and operation but offer basic security measures. This article discusses the three main firewall categories and their deployment modes:
Packet Filtering Firewalls
Like a metal detector at the front of a building, firewalls read data packets at each network level and determine whether to let them into the organization. They do so by assessing information about the packages, such as their source and destination addresses and predefined rules that indicate which activities are permitted.
The earliest types of firewall software, packet filtering firewalls, create checkpoints in routers and switches to quickly and easily approve or deny traffic without consuming significant computing resources. This firewall is an effective deterrent for most common attacks, such as phishing.
A packet-filtering firewall compares packet headers — the information that tells each packet where to go — with the packet payload or actual user data. It then reforms the data packets according to established rules, which is how it can distinguish malicious content from legitimate activity.
A similar type of firewall, circuit-level gateways, is designed to verify the transmission control protocol (TCP) handshake — which ensures that a connection has a specific source and destination — and can quickly approve or deny it. However, since they do not check the packets’ contents, circuit-level gateways could allow malware through if it has the proper TCP handshake. This is why it is important to pair them with packet inspection technology.
Circuit-level gateways monitor network traffic at the OSI model’s session layer or between the application and transport layers of TCP/IP. They work as handshaking devices between trusted servers and clients with untrusted hosts. They validate connection setup and verify that the transmitted information adheres to security protocols. Once a session has been established, the firewall steps back and only allows data packets associated with the established session to pass through. This helps keep information about the secure network private and prevents data leakage from unauthorized interception.
Like packet filtering firewalls, circuit-level gateways are cost-efficient, simplistic, and barely impact a network’s performance. However, since they don’t inspect the content of data packets, they are vulnerable to malware attacks that exploit the handshake process to enter a secure network. Furthermore, circuit-level gateways must be updated frequently to stay effective against new threats, which takes up the time of onsite security teams.
While circuit-level gateways can be paired with other firewall forms, they are typically used with proxy applications to perform advanced inspection and monitoring of data packets. For example, proxy applications might view common types of data (like HTTP for web pages, SMTP or POP3 for email, and FTP for file transfers) to ensure they comply with internal rules.
Firewalls protect your organization by creating a barrier between internal network devices and incoming external traffic. They carefully analyze incoming data packets and block those that contain malicious code. They also allow specific packages to pass through based on pre-established rules. In addition, firewalls can filter specific types of incoming and outgoing traffic based on the protocol, port, or IP address it uses to communicate with other servers.
Like a metal detector at the entrance of a building, firewalls examine all data packets as they enter or exit a business. They compare those packets against a database of known threats and identify suspicious traffic patterns. This prevents hackers from accessing your organization’s sensitive information and helps mitigate the risk of cyberattacks.
There are a variety of different types of firewalls available to businesses. Each one offers a different set of features, so it’s essential to understand the differences before making a purchase decision. Packet filters are simple but offer limited security, stateful inspection firewalls are more robust but can slow down networks, and application-level gateways are an excellent choice for protecting Web-based applications.
Another option is a next-generation firewall (NGFW). These firewalls can combine several of the other types we’ve discussed, and they often offer advanced intrusion detection/prevention, antivirus features, and application control. Additionally, some NGFWs connect to the cloud security services of their manufacturer to receive threat intelligence updates.
Firewalls have long been the backbone of cybersecurity. However, newer and more sophisticated attacks require a multifaceted approach focusing on all network communication aspects. This is why next-generation firewalls were created.
NGFWs integrate several security technologies into one comprehensive platform to protect against advanced threats like DDoS attacks, malware, and ransomware. The best NGFWs also include the following:
- Integrated web application firewall technology.
- Threat and malware detection.
- Data loss prevention (DLP) capabilities.
Depending on your business needs, you may need to purchase additional licenses for features like network sandboxing or IPS functionality.
The most crucial difference between NGFWs and other types of firewall software is their ability to analyze traffic at the application layer. Unlike traditional firewalls, which are limited to filtering network packets based on their IP and port addresses, NGFWs operate at layers 7 through 9. As such, they can inspect traffic based on the actual contents of each packet.
Moreover, the best NGFWs use intelligence engines to enhance their effectiveness at detecting and preventing incoming threats. For example, an integrated platform boosts its accuracy in spotting the most elusive threats. This feature is crucial for a cybersecurity solution protecting your business from the most sophisticated threats.