Many organisations already have firewalls in place, but that does not mean they are fully protected against distributed denial-of-service attacks. Firewalls and DDoS protection serve related but distinct purposes, and that distinction matters as businesses become more dependent on uninterrupted digital access.
A firewall is primarily a policy control. It decides which traffic should be allowed, which traffic should be blocked, and which parts of a network should remain separated. That makes it an essential part of any security architecture. It helps reduce exposure, enforce access rules, support segmentation, and prevent traffic that clearly violates approved policies from moving through the network.
DDoS protection addresses a different problem. Its role is to preserve availability when hostile traffic is designed to overwhelm bandwidth, infrastructure, applications, or operational teams. A DDoS attack does not always need to bypass security rules to cause disruption. In many cases, the attack works by forcing systems to process more packets, sessions, or requests than they can handle.
This is where firewall-only strategies can create a gap. A firewall may correctly identify and reject unwanted traffic, but it still has to receive that traffic, inspect it, classify it, match it against policy, and then drop it. At high enough volume or frequency, that processing burden can itself become damaging. The firewall may be performing its intended security function while still becoming overloaded.
The risk is particularly relevant for stateful firewalls, which track connection information to make more informed decisions. Under normal conditions, this capability is valuable. During a DDoS attack, however, attackers can exploit that same mechanism by generating large numbers of connection attempts, half-open sessions, or constantly changing flows. The aim is not necessarily to get through the firewall. It may simply be to exhaust connection tables, memory, CPU, or other resources.
If an attack fills the upstream connection before traffic reaches the firewall, the firewall may not be able to protect service availability at all. Users can still be locked out because the path into the network has already been consumed. In that situation, mitigation needs to happen before, at, or alongside the point of congestion, rather than only after the traffic arrives at the firewall.
Dedicated DDoS protection is designed around this availability challenge. It helps detect abnormal traffic patterns quickly, applies automated mitigation, filters floods and multi-vector attacks, and reduces pressure on firewalls and downstream infrastructure. It also improves visibility into attack type, scale, duration, and potential impact, supporting faster decisions during incidents.
Corero Network Security plc (LON:CNS) is a global provider of automated business continuity and network security solutions.
