December 18, 2023

Why Firewalls are Inadequate as Standalone DDoS Solutions

In the realm of distributed denial of service (DDoS) defenses, it is vital to understand that not all solutions are on par. From traditional firewalls to Web Application Firewalls (WAFs) and Content Delivery Networks (CDNs), each safeguard serves a distinct objective, offers potential advantages, and entails inherent risks.

Despite their effectiveness in safeguarding networks against various security issues, traditional firewalls have significant limitations when it comes to defending against DDoS and targeted attacks on servers. In fact, firewalls often act as entry points for DDoS attacks, inadvertently leaving networks vulnerable to denial of service.


Can Firewalls Prevent DDoS Attacks?

While firewalls excel in providing perimeter access control by monitoring and tracking authorized network traffic flows, enabling the smooth passage of legitimate packets and blocking malicious ones from infiltrating your network, their effectiveness in defending against DDoS attacks is limited. Here are key reasons why:


Firewalls are positioned at an inappropriate network location


In network security, it is a common practice to position firewalls behind the border router. However, imagine this: an attack has already breached the network’s perimeter, impacting the network well before the firewall can even begin its mitigation efforts. As the firewall finally springs into action, it’s akin to a valiant knight arriving at the battlefield just as the dust settles - an arrival that is too late, rendering its noble intentions entirely ineffective. A dedicated DDoS mitigation solution, on the other hand, would be strategically deployed prior to the border router, enabling the early detection of an attack.  


Figure 1 - Firewalls are conventionally positioned behind the border router
Figure 1 - Firewalls are conventionally positioned behind the border router


Firewalls are Stateful Devices


Firewalls serve as stateful devices, diligently tracking network connections through connection tables. Each packet undergoes a meticulous matching process against this table, ensuring that it aligns with established and legitimate connections. Typically, these connection tables can handle tens of thousands of active connections, sufficient for regular network operations.

However, the landscape changes dramatically during a DDoS attack, where up to millions of packets bombard the network every second. As the first line of defense, the firewall opens new connections in its connection table for each malicious packet. However, this assault eventually leads to the rapid depletion of the connection table's capacity. Once the connection table reaches its maximum capacity, it denies the establishment of any further connections, ultimately blocking legitimate users from establishing connections.


Firewalls are not designed to handle volumetric attacks


Volumetric attacks such as HTTP/HTTPS floods consist of millions of valid sessions. Individually, each session appears innocuous and cannot be flagged as a threat by firewalls. The inherent limitation of firewalls lies in their original design, which primarily focuses on inspecting individual sessions rather than analyzing the intentions behind millions of concurrent sessions. As a result, this limitation hampers the firewalls' effectiveness in detecting and mitigating attacks that are composed of numerous valid requests.


Why the need for a Purpose-Built Anti-DDoS Solution?

The ever-growing prevalence and complexity of DDoS attacks have undeniably reshaped the security landscape. As organizations adapt their security frameworks to effectively combat the surge in availability-based attacks, it becomes evident that the tools they employ must also evolve in tandem. While firewalls maintain their significance in safeguarding networks, the present-day threats demand a holistic solution that can fortify multiple layers of both the network and applications. Furthermore, this solution must possess the capability to discern between legitimate and malicious traffic, ensuring uninterrupted operation for organizations.


Mitigate DDoS Threats with Confidence

At the heart of Nexusguard's anti-DDoS solutions lies an array of powerful features. From attack traffic detection and mitigation to clean traffic delivery through our fully managed solutions, we offer a robust set of tools to combat DDoS attacks head-on. Our solutions are continuously updated with the latest technologies, including AI-driven algorithms, cyber threat hunting and proactive global threat intelligence, ensuring your defenses stay ahead of the curve, identifying and neutralizing malicious threats swiftly and effectively.

Nexusguard Origin Protection (OP) is a purpose-built service that provides extensive protection for mission-critical services across expansive networks. Specifically tailored to meet the requirements of large-scale environments managing hundreds of Class C networks or even a Class B network, OP serves as a powerful defense against a broad spectrum of L3/4 and L7 attacks. With its comprehensive defense capabilities, OP offers robust protection, effectively addressing the following business availability challenges caused by complex DDoS attacks, including volumetric and protocol-based attacks


Backed by our dedicated Security Operations Center (SOC), we also offer round-the-clock service in multiple languages, with a team of experts who are always ready to assist you with security management and emergency response against cyber attacks. 

With our comprehensive array of capabilities, cutting-edge technologies, and dedicated support, you can stay one step ahead of DDoS threats and focus on what matters most: the success of your business.

Contact us today to bolster your security strategy and safeguard your digital assets.


Firewalls alone won't suffice when it comes to defending against DDoS attacks. Dedicated DDoS protection solutions are essential in today's evolving threat landscape to ensure the resilience of your network and applications.

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