What to Know When Buying a Web Application Firewall Solution for Business Security

Ben Rees, Senior Network Product Engineer | Average Read Time: 13 minutes

A web application firewall (WAF) is one of the most important security investments you can make for your business. As web applications become primary targets for cyber attacks, choosing the right WAF determines whether your organisation is protected or exposed.

Every day, attackers probe web applications with SQL injection attempts, cross-site scripting exploits, credential stuffing, and DDoS floods. A web application firewall sits between your applications and the internet, inspecting traffic and blocking malicious requests before they reach your systems. For any organisation with public-facing digital services, WAF protection isn't optional.

But buying a web application firewall is more complicated than it first appears. The market is crowded with options, each promising comprehensive protection. Some organisations invest heavily in WAF technology only to discover it creates blind spots elsewhere. Others configure their solution once and assume they're protected, not realising that default settings leave critical gaps.

This guide explains what a WAF does, what to look for when evaluating options, and how to avoid the mistakes that undermine your investment. Whether you're securing NHS patient portals, financial services platforms, council services, or commercial applications, understanding these fundamentals will help you decide that genuinely strengthens your security posture.

Key takeaways: what to know when buying a WAF

• A web application firewall protects against application-layer attacks including SQL injection, cross-site scripting (XSS), DDoS, and bot attacks

• Choose your deployment model based on your infrastructure: cloud-based WAFs offer speed and scalability, on-premise WAFs provide control, hybrid approaches suit complex environments

• Evaluate integration capabilities with your existing SIEM, identity management, DevOps pipelines, and network infrastructure

• Avoid common pitfalls: don't rely on default settings, ensure visibility into what's being blocked, and match the solution to your operational capacity

• Consider managed WAF services if your team lacks dedicated application security specialists

• Your WAF should complement broader security controls, not operate in isolation

What is a web application firewall?

A web application firewall is a security solution that monitors, filters, and blocks HTTP/HTTPS traffic to and from web applications. Unlike traditional network firewalls that operate at the network layer, a WAF works at the application layer (Layer 7 of the OSI model), giving it visibility into the actual content of web requests.

This distinction matters. Next-generation firewalls can inspect traffic, including HTTPS, using deep packet inspection; however, they're designed for general network security rather than specifically for web application protection. A WAF is a specialist tool, purpose-built to understand web application logic, parse HTTP requests in detail, and defend against attacks that exploit application-layer vulnerabilities.

When someone attempts an SQL injection attack by embedding database commands in a form field, a WAF recognises the signature and blocks the request. When a bot attempts to overwhelm your login page with credential stuffing attacks, a WAF can identify the abnormal behaviour and throttle or block the traffic.

How does a WAF work?

Web application firewalls use several detection methods, often in combination:

Signature-based detection compares incoming requests against a database of known attack patterns. This approach effectively blocks documented vulnerabilities and common attack techniques. The limitation is that new, unknown attacks (zero-day exploits) won't match existing signatures until the database is updated.

Behavioural analysis monitors traffic patterns and flags anomalies. If your application typically receives 100 login attempts per hour and suddenly sees 10,000, behavioural analysis identifies this as suspicious, even if each individual request appears legitimate. This method catches attacks that signature-based detection might miss.

Positive security models define what legitimate traffic looks like and block everything else. Rather than trying to identify every possible attack, this approach specifies the acceptable parameters, formats, and values for each application endpoint. Anything that doesn't conform gets blocked. This is more restrictive but provides stronger protection against unknown threats.

Most modern WAFs combine these approaches, using signatures for known attacks, behavioural analysis for anomalies, and allowing administrators to define positive security rules for critical applications.

Common threats a WAF protects against

Understanding what a WAF defends against helps clarify why it's essential for organisations with public-facing applications.

SQL injection

SQL injection attacks occur when attackers insert malicious database commands into input fields, exploiting applications that don't properly validate user input. A successful SQL injection can expose entire databases, including customer records, credentials, and sensitive business data. WAFs identify SQL syntax in request parameters and block these attempts before they reach your application.

Cross-site scripting (XSS)

XSS attacks inject malicious scripts into web pages viewed by other users. These scripts can steal session cookies, redirect users to phishing sites, or modify page content. WAFs detect script tags and JavaScript code in unexpected locations within requests, preventing these payloads from executing.

DDoS attacks

Distributed denial-of-service attacks flood applications with traffic, overwhelming resources and making services unavailable. While dedicated DDoS mitigation solutions handle volumetric attacks at the network level, WAFs address application-layer DDoS by identifying and blocking request patterns designed to consume server resources, such as complex database queries or resource-intensive page requests.

Bot attacks

Automated bots probe applications for vulnerabilities, scrape content, stuff credentials, and conduct reconnaissance. WAFs can distinguish between legitimate users and automated traffic based on request patterns, timing, and behaviour, blocking malicious bots while allowing search engine crawlers and other beneficial automation.

API abuse

As organisations expose more functionality through APIs, these interfaces become attractive targets. WAFs can enforce rate limits, validate request structures, and ensure API calls conform to expected patterns, protecting against abuse and exploitation.

Key considerations when buying a WAF

The WAF market offers numerous options with varying capabilities, deployment models, and price points. These factors should guide your evaluation.

WAF deployment models: cloud, on-premise, or hybrid

WAFs can be deployed in several ways, each with distinct advantages and trade-offs.

Cloud-based WAF

Cloud-based WAFs are delivered as a service, with traffic routed through the provider's infrastructure before reaching your applications. This model offers rapid deployment, automatic updates, and scalability without hardware investment. It's particularly suited to organisations with limited security staff or those running applications across multiple cloud environments. The trade-off is that you're dependent on the provider's infrastructure and may have less granular control over configuration.

On-premise WAF

On-premise WAFs run on hardware or virtual appliances within your data centre. This approach gives you complete control over configuration and keeps traffic within your environment. It's often preferred by organisations with strict data sovereignty requirements or existing investments in data centre infrastructure. The trade-off is greater operational overhead: you're responsible for maintenance, updates, and scaling.

Hybrid WAF deployment

Hybrid approaches combine elements of both. You might deploy on-premise WAFs for applications in your data centre while using cloud-based protection for SaaS applications and public-facing services. This flexibility suits organisations with complex hybrid environments.

Choosing the right deployment model

Consider where your applications run, how your traffic flows, and what level of control you need. A cloud-first organisation with applications distributed across AWS, Azure, and SaaS platforms will likely benefit from cloud-native WAF capabilities. An organisation with significant on-premise infrastructure and compliance requirements around data handling might prioritise on-premise deployment.

Scalability and performance under load

Your WAF needs to handle traffic spikes without becoming a bottleneck. Evaluate how the solution scales under load. Cloud-based WAFs typically scale automatically, absorbing traffic spikes without intervention. On-premise solutions require capacity planning and may need additional hardware to handle growth.

Ask vendors about throughput capacity, latency impact, and how the solution performs during DDoS attacks. A WAF that can't keep pace with legitimate traffic during peak periods will frustrate users and potentially impact revenue.

Integration with existing security infrastructure

A WAF doesn't operate in isolation. It needs to work with your broader security ecosystem.

SIEM integration

H4 SIEM integration allows your WAF to feed logs and alerts into your security information and event management platform, providing correlated visibility across your environment. Ensure the WAF supports standard log formats (CEF, SYSLOG) and can stream events to your chosen SIEM solution.

Identity and access management

Identity and access management integration enables the WAF to make decisions based on user identity, not just IP addresses. This supports more granular policies and helps distinguish between legitimate users and attackers using compromised credentials.

DevOps and CI/CD pipelines

DevOps and CI/CD pipeline integration matters if your development teams deploy frequently. WAF rules should be version-controlled and deployable alongside application code, preventing security from becoming a bottleneck in your release process.

Network infrastructure compatibility

Network infrastructure compatibility is essential. Your WAF must work with your existing load balancers, CDNs, and network architecture. Verify that the solution supports your SSL/TLS configuration and can handle your certificate management approach.

Automation, analytics, and threat intelligence

Manual security operations don't scale. Look for WAFs that offer:

Automated rule updates

Automated rule updates incorporate new threat intelligence without manual intervention. Attack techniques evolve constantly, and your defences need to keep pace.

Machine learning capabilities

Machine learning capabilities identify emerging threats based on behavioural patterns, rather than relying solely on known signatures.

Comprehensive analytics

Comprehensive analytics provide visibility into attack trends, blocked requests, and application performance. You should be able to understand what's being blocked, why, and whether legitimate traffic is being affected.

Real-time alerting

Real-time alerting notifies your security team of significant events without overwhelming them with noise. Configurable thresholds and intelligent alert aggregation help teams focus on genuine threats.

Managed vs self-managed WAF: understanding operational requirements

A WAF isn't a "set and forget" solution. Applications change, new vulnerabilities emerge, and attack techniques evolve. Consider the operational burden each option creates.

Managed WAF services

Managed WAF services handle rule maintenance, tuning, and monitoring on your behalf. This approach reduces operational overhead but may offer less flexibility. It's well-suited to organisations without dedicated application security specialists.

Self-managed WAF solutions

Self-managed solutions give you complete control but require skilled staff to maintain, tune, and monitor the WAF effectively. Misconfigured rules can block legitimate traffic or create security gaps.

Be realistic about your team's capacity. A sophisticated WAF that sits misconfigured because no one has time to manage it provides less protection than a simpler, well-maintained solution.

Compliance, reporting, and audit requirements

Regulated industries need WAFs that support compliance requirements. Evaluate reporting capabilities against your specific obligations.

For NHS and healthcare organisations, this means demonstrating protection of patient data and meeting NHS Digital security standards. For financial services, PCI DSS requirements demand specific logging and protection capabilities. Public sector organisations working with sensitive data need audit trails that satisfy their regulatory framework.

Look for WAFs that provide compliance-specific reporting templates and retain logs for the duration your regulations require.

Common pitfalls to avoid

Many WAF implementations fail to deliver their promised protection. Understanding common mistakes helps you avoid them.

Over-reliance on default settings

WAFs ship with default rule sets designed to work across a range of applications. These defaults provide baseline protection but rarely match your specific applications perfectly. They may block legitimate functionality or miss application-specific vulnerabilities.

Invest time in tuning your WAF to your applications. Analyse false positives and adjust rules accordingly. Create custom rules for application-specific risks. A tuned WAF provides significantly better protection than one running default configurations.

Lack of visibility

Some organisations deploy a WAF and assume they're protected, without monitoring what it's doing. They discover problems only when users complain about blocked legitimate requests or when a breach investigation reveals the WAF wasn't blocking attacks they assumed it would catch.

Establish dashboards that show WAF activity, review blocked requests regularly, and investigate anomalies. Your WAF should contribute to your security visibility, not operate as a black box.

Choosing a tool that doesn't align with business objectives

Technical capabilities matter, but they must support business goals. A WAF that provides excellent protection but creates unacceptable latency for customer-facing applications fails the business. A solution that requires constant manual intervention from a team that doesn't have capacity creates risk rather than reducing it.

Start with your business requirements: What applications need protection? What's the acceptable latency? Who will manage the solution? What compliance requirements apply? Then evaluate WAF options against these criteria.

Ignoring the broader security context

A WAF addresses application-layer threats but doesn't solve all security challenges. Organisations sometimes invest heavily in WAF technology while neglecting network security, endpoint protection, or secure connectivity.

Application security requires a layered approach. Your WAF should complement, not replace, other security controls. Consider how it fits within your broader security architecture and where gaps might remain.

Failing to plan for hybrid environments

Modern organisations rarely run all applications in a single location. You likely have some applications in your data centre, others in public cloud, and SaaS solutions accessed by users everywhere. A WAF strategy that only addresses on-premise applications leaves cloud workloads exposed.

Plan for protection across your entire application estate. This might mean multiple WAF deployments, a cloud-based solution that can protect distributed applications, or integration with cloud-native security services.

How Cloud Gateway adds value

Web application firewalls don't exist in isolation. They're one component of a comprehensive approach to securing your digital estate. How your WAF connects to your broader network infrastructure, how traffic flows between your applications, users, and cloud environments, and how you maintain visibility across this complexity all determine whether your security investments deliver real protection.

Cloud Gateway's platform brings connectivity, security, and observability together in a way that complements and enhances your WAF investment.

Secure connectivity across hybrid environments

Many organisations struggle with fragmented security when applications span on-premise data centres, multiple cloud providers, and SaaS platforms. Traffic takes different paths, security policies are inconsistent, and visibility is incomplete.

Cloud Gateway's Secure Fabric provides a unified backbone that connects your entire digital estate. Whether traffic is destined for applications protected by cloud-native WAFs, on-premise security stacks, or third-party services, it flows through consistent security controls. This eliminates the gaps that attackers exploit when organisations have inconsistent protection across different environments.

Integrated WAF and complementary security capabilities

Cloud Gateway's platform includes Web Application Firewall capabilities as part of a broader security suite. Combined with Firewall-as-a-Service (FWaaS), Secure Web Gateway (SWG), and next-generation firewall features, organisations get layered protection that addresses threats across the stack.

This integrated approach means security policies are consistent, visibility is complete, and management is simplified. Rather than operating separate solutions for application security, network security, and web filtering, everything operates through a single platform.

Real-time visibility and unified control

The unified control plane provides a single interface for monitoring security across your environment. You can see traffic flows, review security events, analyse threats, and adjust policies without switching between multiple tools.

For WAF specifically, this means logs and events integrate with your broader security visibility. When an application-layer attack targets your web applications, you see it in context with network traffic, user activity, and other security events. This correlated view accelerates threat detection and response.

Managed WAF service with UK-based expertise

Cloud Gateway operates as a managed service provider, meaning our UK-based engineers handle the operational burden of maintaining and optimising your security controls. For organisations without dedicated application security specialists, this ensures your WAF and other security components are properly configured, tuned, and monitored.

This doesn't mean sacrificing control. The platform provides portal-level visibility and self-serve capabilities when you want them, with expert support available when you need it. You choose the operating model that fits your organisation.

Compliance-ready infrastructure for regulated industries

For NHS trusts meeting HSCN requirements, public sector organisations requiring PSN compliance, or financial services firms addressing regulatory obligations, Cloud Gateway's platform is built with compliance in mind. ISO 27001, ISO 9001, Cyber Essentials Plus, and PCI DSS certifications provide assurance that the infrastructure supporting your security controls meets rigorous standards.

All data and operations remain within the UK, addressing data sovereignty requirements that matter to regulated industries.

The right decision

Buying a WAF is a significant investment. The right choice protects your applications and supports your business. The wrong choice creates false confidence, operational headaches, or both.

Start with a clear understanding of what you're protecting and why. Map your applications, identify the threats they face, and define the compliance requirements that apply. Evaluate WAF options against your actual business needs, not just technical feature lists.

Consider the operational model that fits your organisation. If you have skilled security staff and want maximum control, self-managed solutions may be appropriate. If your team is stretched and you need expert support, managed services reduce risk.

Think about how a WAF fits your broader security architecture. It should complement network security, secure connectivity, and observability capabilities, not operate as an isolated tool.

And remember that security is ongoing. Applications change, threats evolve, and your protection needs to keep pace. Choose a solution you can maintain effectively over time, whether that means investing in internal expertise or partnering with specialists who can manage it on your behalf.

Cloud Gateway helps organisations navigate these decisions. Our consultative approach starts with understanding your environment, your challenges, and your objectives, then designs solutions that genuinely address them. We make change easy, providing the expertise and platform capabilities to secure your applications without adding complexity to your operations.

If you're evaluating WAF options and want to understand how secure connectivity and integrated security services could strengthen your approach, get in touch. We'll help you cut through the complexity and find a solution that works.