WAFs (Web Application Firewalls) are security tools used to ward off attacks at OSI model Layer 7, the application layer. Working much like reverse proxies, WAFs intercept traffic from clients while simultaneously protecting servers against attack.

WAFs operate using policies – set of rules which can quickly be changed in response to different attack vectors in DDoS attacks or other scenarios.

What is a WAF?

WAFs filter incoming traffic using known attack signatures, application profiling, artificial intelligence (AI), custom rules and contextual data in order to detect and stop web attacks. These tools help organizations protect themselves against attacks targeting OSI Model Layer 7 — or application level — such as SQL injection and cookie manipulation techniques that bypass traditional network firewall security measures.

WAFs use either a blocklist or allowlist security model. A blocklist works similar to an exclusive club in that those who do not meet dress code will be denied entrance, while allowlist allows only traffic that complies with preapproved rules in its rule set, helping prevent zero-day attacks as well as accessing sensitive data such as cardholder data (CHD). There are WAF solutions available both on-premises, in the cloud, with self-managed or fully managed deployment models; which one best meets your business and resources will depend on which deployment model best meets them all.

WAF Basics

WAFs protect web applications from various threats at OSI Model Layer 7 (the application level). For instance, if an attacker attempts to bypass authentication by creating new SQL syntax to gain access to sensitive information without authentication, a WAF could detect and prevent it.

To detect attacks, the WAF monitors HTTP traffic between browser and application server, looking out for suspicious requests with suspicious characteristics that indicate possible attacks. When this occurs, anomaly scoring assigns scores for each deviation from normal traffic flow with higher scores indicating more serious deviations such as attempts at SQL injection.

The WAF can then choose to allow or block this traffic based on its policy; alternatively, if security checks determine that a Referer header contains malicious domains, conditionals could be added that restrict all but this traffic from going through.

WAF Security

Not only are the best WAFs capable of detecting and blocking attacks, they also include an intelligence engine which triages incoming traffic based on known attack signatures, AI/ML analysis, application profiling and custom rules to reduce false positives and ensure legitimate traffic does not get blocked. This helps prevent false positives while simultaneously guaranteeing legitimate traffic does not get stopped by mistake.

WAFs are essential components of any digital bank or e-commerce website that interact directly with their customer base, such as cross-site scripting (XSS), SQL injection and distributed denial of service attacks that target application layers.

Network-based WAFs operate at OSI model layer 7 to protect application-layer protocols like HTTP and HTTPS from attacks such as cross-site scripting, cookie manipulation, API manipulation and brute force assaults as well as volumetric DDoS attacks aimed at the application layer. Host-based WAFs installed in server layers may cause performance degradation and require management overhead;

WAF Deployment

WAFs filter out malicious traffic from web applications, making it harder for attackers to identify exploitable flaws in these systems. They act like screens allowing in friendly traffic but blocking any that may pose threats.

Installing security appliances into your infrastructure has its own set of advantages and disadvantages that depend on factors like infrastructure requirements, management capacities, architectural flexibility and architectural scalability.

WAFs employ behavioral learning techniques to detect suspicious patterns in application interactions and can detect more sophisticated attacks than IPS solutions, while also offering greater flexibility when adapting rules in response to evolving threats or changes in architecture.

Host-based WAFs require software integration and may be more costly to manage and scale; however, they can protect applications without access to their source code. Cloud-based WAFs often provide easier deployment, scalability and low latency than their host counterparts.