A Web Application Firewall (WAF) is a type of firewall that specializes in protecting web applications from various security threats. In contrast to traditional firewalls, which filter and control data traffic at network level, a WAF focuses specifically on the application level and protects web applications from attacks that target vulnerabilities in the application logic.
A WAF works by monitoring and analyzing incoming and outgoing traffic to a web application to detect and block potential security threats before they can harm the application.
The WAF is positioned between the Internet and the web application, usually directly behind the network router. It acts as a gateway for all incoming and outgoing requests and responses. All HTTP requests to the web application first pass through the WAF before being forwarded to the application. Similarly, all responses from the application are sent back to the user via the WAF.
The WAF uses a set of predefined and/or customizable rules to analyze data traffic. These rules are designed to identify known attack patterns and suspicious behavior. Some examples of such rules are:
The WAF filters data traffic based on the defined rules. It can block or redirect requests or issue special challenges (e.g., CAPTCHA) to distinguish real users from bots. The actions that the WAF performs based on the rules can be either block, allow, log, or alert.
Modern WAFs often offer machine learning or adaptive capabilities to detect new threats that may not be included in static rule sets. These systems can monitor traffic and recognize patterns that indicate anomalous or potentially dangerous activity and adjust security rules accordingly over time.
The WAF can provide different types of protection mechanisms, including:
The WAF logs all incidents and can generate detailed reports on attack attempts and security events. Administrators can receive notifications about incidents so they can react quickly.
A Web Application Firewall offers protection against a variety of threats and attacks that specifically affect web applications.
SQL injection
In an SQL injection, an attacker inserts malicious SQL code into an input, which is then executed by the server. This can lead to confidential data being disclosed, changed, or deleted. A WAF can recognize and block such inputs.
Cross-site scripting (XSS)
XSS attacks occur when an attacker embeds malicious code, typically JavaScript, into a website, which is then executed in users’ browsers. This can be used for data theft, session hijacking, and other malicious activities. A WAF can filter incoming and outgoing content to prevent such attacks.
Cross-site request forgery (CSRF)
In a CSRF, an attacker manipulates a user to perform unwanted actions on a web application while logged in. A WAF can recognize and prevent such requests by ensuring that each request comes from the expected source.
File inclusion
In file inclusion attacks, an attacker attempts to execute scripts on the server by injecting files into the application. A WAF can monitor paths in requests and block unauthorized access to system files.
DDoS attacks (Distributed Denial of Service)
While a Web Application Firewall is not primarily designed to provide comprehensive DDoS protection, it can help mitigate application-layer DDoS attacks, where a high number of requests are sent to specific parts of a web application to overload it.
Vulnerabilities in the application
WAFs can protect against exploits that target known vulnerabilities in software, such as CMS (content management systems) and their plugins.
Identity theft and session hijacking
WAFs can improve the protection of user sessions and authentication data by blocking attack attempts aimed at stealing or manipulating session IDs.
Unknown threats and zero-day attacks
Modern WAFs use machine learning and behavioral analysis to detect unknown threats and zero-day attacks that are not yet listed in security databases.
By monitoring traffic and enforcing security rules, a WAF therefore provides critical protection for web applications against a variety of attack vectors.
Web Application Firewalls (WAFs) can be classified according to their implementation type and the underlying technology approach. The primary WAF types include:
Network-based WAFs
Network-based WAFs are hardware-based solutions that are physically integrated into the company’s data center or network infrastructure. They are particularly effective in environments that require high speeds and low latency. As they run on dedicated hardware, they often offer very good performance, but are generally more expensive to purchase and maintain.
Host-based WAFs
Host-based WAFs are software solutions that are installed directly on the server on which the web application is running. They can be configured specifically for the needs of a particular application and are often less expensive than hardware-based solutions. However, they can affect the performance of the host server and require careful maintenance and configuration.
Cloud-based WAFs
Cloud-based WAFs are offered as a service by a third-party provider and are accessible via the Internet. These WAFs are easy to implement and scale as the provider takes care of maintenance, updates, and scaling. They are cost-effective and provide protection against a wide range of attacks, including large DDoS attacks. However, they require a constant Internet connection and can pose privacy concerns because traffic is routed through external data centers.
Hybrid WAFs
Hybrid WAFs combine elements of network and host-based or cloud-based models to take advantage of both approaches. For example, they can be implemented in on-premise hardware, while some functions are outsourced to the cloud to improve flexibility and scalability.
With the special Zero Touch WAF from Link11, you not only protect yourself effectively and automatically against zero-day vulnerabilities or the OWASP Top 10 threats, but also benefit from maximum flexibility thanks to the whitelisting approach. If you have any questions about this security solution, our security experts will be happy to help you at any time.
