Understanding the Key Differences Between WAF and Firewall

Firewalls protect networks from unauthorized access and certain types of malicious attacks. WAFs complement traditional network firewalls by adding web application security capabilities, including device fingerprinting, behavioral algorithms, bot management and mitigation, and dedicated API protection.

A WAF explicitly protects a business’s web applications and internet-facing zones from threats like cross-site scripting (XSS), SQL injection, and DDoS attacks. Understand the critical differences between a WAF and a firewall to build a robust cybersecurity infrastructure.


WAFs are positioned in front of web apps

While a firewall filters general network traffic, a WAF focuses solely on the language of web applications, analyzing HTTP requests for signs of SQL injection, cross-site scripting, and other nefarious payloads. This laser-sharp focus, a vital aspect of the WAF vs firewall difference, allows the WAF to neutralize threats that bypass traditional firewalls effectively.

WAFs position between your web applications and users to monitor traffic between both parties. They analyze this traffic, comparing it against vulnerability databases and blocking any packets that are identified as malicious. As a result, they can protect your web apps from attacks that can evade traditional firewalls.

By default, most top WAFs use a rule set, including signature detection (pattern matching), to identify and block attacks. This is effective against known and common threats such as SQL injection, cross-site scripting, and application-layer denial of service (ApDoS) assaults. Other features are also available depending on the WAF you choose. For example, some WAFs feature a rule set that uses anomaly detection to detect and stop attacks that don’t match known attack patterns.

Other WAFs offer features such as sanitization, which converts potentially malicious data into harmless information. These are useful for combating attacks that target specific data types, such as credit card numbers. Some WAFs enable businesses to log all or select levels of potentially malicious requests, which can be helpful for security teams looking for more insight into their cyber defenses.


WAFs can inspect HTTP traffic

A WAF can filter and monitor the traffic that connects to a web application. It can be a hardware appliance or a software plugin installed on a server. It can also be deployed as a cloud-based service. Regardless of the implementation type, the primary function of a WAF is to prevent the vulnerabilities and flaws in a web application from being exploited by attackers.

A WAF also analyzes the traffic sent to a web app, which can help it identify the attackers’ intent. For example, if an SQL injection attack hits a web app, a WAF can recognize and protect the attack. This type of targeted protection is essential for businesses that use web applications to house sensitive data, like customer information and credit card details. Unlike traditional firewalls, which guard against unauthorized access to your network by ports and protocols, WAFs zoom in on individual web applications to protect them against specific vulnerabilities that attackers could exploit.


WAFs can block traffic

A WAF is a network firewall that protects web applications from attack. This capability is essential for businesses because it prevents attackers from exploiting vulnerabilities in web applications, exposing the broader business network to attacks. However, a WAF is not an end-all solution to cyberattacks. It cannot prevent threats that originate at the network layer, and it may not stop some social engineering or email phishing attacks, which require other solutions such as user awareness training and advanced threat detection systems.

A WAF intercepts and inspects all HTTP communication between clients and web applications to detect and block traffic. This is done by examining every aspect of the request, including parameters and behavioral patterns. It also performs various tests, such as device fingerprinting, input device analysis, and CAPTCHA challenges, to determine whether a request is legitimate.

A WAF can follow a negative security model, which blocks all traffic that does not match specific rules or signatures, or a positive security model, which allows all valid inputs and then performs a series of validations to determine malicious ones. Many WAFs utilize a combination of both models. This method provides more flexibility and protection than blocking everything with a single negative signature. Some newer models use machine learning to detect and update positive signatures based on real-world activity and vulnerabilities.


WAFs are more flexible

WAFs are more flexible than firewalls when allowing or blocking web traffic. They can be configured to allow or block specific attacks that exploit security vulnerabilities. They can also be configured to monitor traffic and record and report on endpoints that have been visited. This flexibility allows organizations to customize the way they protect their applications and enables them to respond quickly to threats and incidents.

Most WAFs use rules to filter incoming and outgoing web traffic. The rules can be based on anomaly detection, machine learning, or both. They are designed to prevent Open Worldwide Application Security Project (OWASP) top vulnerabilities such as SQL injection and cross-site scripting (XSS).

Some WAF solutions run in the cloud as fully managed services or on hardware appliances installed in on-premise data centers. Others are self-managed and require a network administrator to deploy, configure, and manage them. Cloud WAFs are a popular choice as they provide a low-cost option, are easy to deploy, and are automatically provisioned with networking policies that match the environment in which they operate.

One disadvantage of WAFs is that they can introduce performance latency because they sit in line between users and applications. The amount of latency introduced depends on how the WAF is deployed and the complexity of the security policies.

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