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What Is A Web Application Firewall?

A web application firewall also known as WAF is basically an online security solution that analyses and blocks the bad web traffic between the clients and the web application.

WAF, website security

An Insight

The traditional security techniques like intruder detection systems (IDS), network firewalls, intrusion prevention systems (IPS) do a good job at blocking the illegitimate traffic and safeguarding your website at the network level. But these techniques do not have the ability to detect and block malicious activities like SQL injection, cross-site scripting (XSS), session hijacking and other such attacks that result from the vulnerabilities present in the web applications.

The web application firewall provides an efficient and all-inclusive security solution in terms of detecting the threats by analyzing the incoming HTTP requests before they reach the server. A WAF has the ability to detect and block the malicious attacks that are imbibed into the safe-looking website traffic that might have passed through the traditional security solutions. Web application firewalls are also useful for the organizations to comply with the HIPAA and PCI-DSS standards.

How Does A Web Application Firewall Work?

The web application firewall is deployed as a hardware that is in tune with the web server or server plugin that directly runs on the web servers. A WAF intercepts all the HTTP requests and scrutinizes each one of them before they are processed further and reach the web server. It scams the GET and POST requests while applying the defined rules in order to detect and block the illegitimate traffic.

On the basis of the selected options for the WAF, the traffic is analyzed and blocked by the WAF and it also challenges the visitors by asking them to enter a CAPTCHA code or by instructing the server to replicate an attack. The blocking and challenging options that are defined prevent any kind of illegitimate traffic from reaching to the web server.

The Operations Of A Web Application Firewall Are Based On 3 Security Models Mentioned Below:

Blacklist or negative security model : This model utilizes the generic signatures for safeguarding the website against the known attacks and it also makes use of some specific signatures for blocking the attacks that might result due to any vulnerability in the web application.

Whitelist or positive security model : This model utilizes the signatures and at times it makes use of additional logic in order to permit only that traffic that meets certain criteria. An example of this is allowing only the HTTP GET requests made through a specific URL and blocking all other traffic.

Hybrid security model : This model is applicable to both the positive and negative models.

Some of the configurable options of a WAF include blocking the session, blocking the request, blocking the user, blocking the IP address or logging the user out.

Related- Hardware Firewall- An Overview


A web application firewall is an efficient solution for preventing the attacks targeted at the web applications but this solution is still evolving. As there is no one tool that can manage all the vulnerabilities present in the web-based applications, it is advisable to use more than one security solution.

A general approach is to combine WAF with DAST (Dynamic Application Security Testing). The DAST tools are created in order to look for signs of security vulnerabilities in the running web applications. This is done by sending requests that look similar to a hacker’s activities to the running web application.

A WAF also comprises of other options and operational models for safeguarding different kinds of websites. Apart from protection, a WAF also provides additional features like compression, caching, SSL acceleration, load balancing and connection pooling that enhances the reliability and performance of a website.

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