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Exploring the Differences Between WAFs and Firewalls

WAFs rely on an attack signature database and block access to known threats. Some also use an allow list approach, which admits traffic based on positive security models.

Regardless of their approach, most WAFs analyze HTTP conversations to reduce or eliminate malicious activities and traffic before reaching servers for processing. This is important for any company that provides web-based products or services such as ecommerce, online banking, and social media platforms.


What is the difference between WAF vs firewall? A WAF can be software, an appliance, or a service that analyzes the components of an HTTP conversation to identify potentially malicious activity. Specifically, it protects against threats such as cross-site request forgery (XSS) attacks, distributed denial of service attacks, and SQL injection attacks that leverage application vulnerabilities.

WAFs can operate in an allowlist or blocklist security model, which requires the use of managed rules and can include an application profiling engine that can be customized to an organization’s needs. A correlation engine that analyzes incoming traffic and triages it using known attack signatures, AI/ML analysis, and custom rules also helps prevent false positives by identifying patterns that indicate a potential threat.

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Unlike network firewalls, which concentrate on layers 3 (network) and 4 (transport), WAFs are deployed in layer 7(applications) of the Open Systems Interconnection (OSI) model. This makes them distinct from traditional firewalls because they are designed to protect web applications and APIs from the wide variety of threats and vulnerabilities in this layer.

As a result of their unique deployment model, WAFs can offer granular security features that address API-specific vulnerabilities, such as rate limiting and support for different data formats. This is one of the main reasons they are considered more effective at protecting applications against web-related attacks than a general network firewall solution.


Web application firewalls (WAF) protect business-critical web applications, web servers, and web-based APIs from advanced attacks. These cyberattacks differ from network firewall protection, operating at OSI model layer 7 (the application level) rather than layers 3 and 4.

A WAF can be software, an appliance, or a service that filters HTTP traffic passing between web browsers and web servers to identify and block malicious requests, preventing the transfer of sensitive data. The way it works is that a WAF acts as a reverse proxy and analyses the communication between web users and web applications to detect malicious patterns and anomalies. It uses a combination of factors, including known attack signatures, AI/ML analysis, application profiling, and custom rules, to determine whether or not an incoming request is malicious. If it is, it may be blocked outright or flagged and tested with a CAPTCHA test to confirm that it’s human and not automated traffic.

A WAF can also integrate with a cloud-based distributed denial of service (DDoS) protection platform to switch over traffic from the vulnerable server to the DDoS system, which can handle large volumetric attacks. Some cloud WAF solutions are content delivery networks (CDNs), offering faster website performance by caching the data closer to web users worldwide.

Operating Location

WAFs are designed to monitor and filter application traffic, ensuring web applications’ integrity, confidentiality, and availability. They can be deployed as an appliance, a host-based solution, or as part of a firewall.

A WAF can be configured to operate based on a positive or negative security model. A blocklist WAF denies access to known attacks by establishing a list of things to exclude (think of the bouncer at an exclusive club). An allowlist WAF admits traffic pre-approved by an index (consider the club’s dress code rules). Many WAFs take a hybrid approach, applying both block and allowlists.

Network-based WAFs are physical hardware appliances pre-loaded with dedicated WAF software installed on a network and configured to protect web applications hosted on the same network. Network-based WAFs provide latency reduction benefits because they are installed close to the web application server and can process traffic without sending it to the internet. Network-based WAFs are also more customizable and can be tuned to target specific threats against a particular application.

A cloud-based WAF is a service offered by a third-party provider. Cloud-based WAFs are typically scalable and can be tailored to fit the needs of high-traffic websites and applications. Most cloud-based WAFs provide a low monthly fee and a fast response time to new threats.


A WAF analyzes HTTP conversations, looking for patterns that indicate malicious activity, and blocks the traffic before it reaches the web application. This protects against cross-site scripting (XSS) attacks, SQL injection, denial of service (DoS) attacks, and command and control communications.

Historically, WAFs relied on databases of attack patterns and security rules to identify malicious traffic. However, this approach could not adapt and stay nimble enough to thwart evolving attacker strategies.

As an alternative, modern WAFs can use AI/ML to detect a broad range of threats through behavioral analysis. They compare traffic patterns with baselines and capture anomalies that might signal an attack. As a result, they can weed out newer, unknown attacks.

WAFs can be deployed on-premises or in the cloud. Some support a transparent bridge mode that allows them to operate within the same ports as the web applications they protect. These WAFs are less expensive than network-based solutions but can be challenging to install and manage. Host-based WAFs, on the other hand, are fully integrated into the software that they protect. They are cheaper than network-based solutions but require extensive local server resources and can be complex to configure. They also need more customization capabilities and require skilled administrators to manage.