A Guide To Web Application Firewall

A web application firewall (WAF) is a type of firewall that monitors, filters, and stops data packets between a website or web application and the outside world. A WAF can be network-based, host-based, or cloud-based, and is frequently installed in front of one or more websites or apps through a reverse proxy. The WAF inspects each packet and employs a rule base to evaluate Layer 7 web application logic and filter out potentially dangerous traffic that might aid web attacks. It can be deployed as a network appliance, server plugin, or cloud service.

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Importance of a Web Application Firewall

A WAF is critical for the expanding number of businesses that sell products or services through the internet, such as online banks, social media platform providers, and mobile application developers, since it helps prevent data leakage. Significant amounts of sensitive data, such as credit card information and client details, are held in back-end databases accessible via web applications. Attackers commonly target these programs in an attempt to obtain access to the data linked with them.

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Banks, for example, may utilise a WAF to assist them in meeting the Payment Card Industry Data Security Standard (PCI DSS), which is a collection of standards designed to safeguard cardholder data (CHD). Installing a firewall is one of the PCI DSS compliance standards’ twelve requirements. This regulation applies to all businesses that handle CHD. Due to the expanding use of mobile applications and the internet of things (IoT), an increasing number of transactions occur at the application layer via the web. As a result, a WAF is a critical component of a contemporary business’s security approach.

While a WAF is critical, it is most successful when used in conjunction with other security components, such as intrusion prevention systems, intrusion detection systems, and traditional or next-generation firewalls (NGFWs). In an ideal world, a WAF would be deployed with other firewall types, such as NGFWs, and security components, such as IPSes and IDSes, which are frequently incorporated in NGFWs.

Types of Web Application Firewall

– Network-based WAFs are often hardware-based and can significantly minimise latency due to the fact that they are installed on-premises through a dedicated appliance as near to the application as feasible. The majority of significant network-based WAF solutions provide rule and configuration replication over several appliances, enabling large-scale deployment, setup, and management. The primary disadvantage of this sort of WAF product is the expense — there is an initial capital investment and continuing operational expenditures for upkeep.

– Some WAFs are host-based can be entirely incorporated into the application’s code. Cost savings and more customisation choices are two advantages of a host-based WAF deployment. Host-based WAFs might be difficult to administer due to the fact that they require application libraries and rely on local server resources to function properly. As a result, more personnel resources, such as developers, system analysts, and DevOps/DevSecOps, may be required.

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– Cloud-hosted WAFs are an affordable option for enterprises looking for a turnkey solution that requires minimum deployment and administration resources. Cloud WAFs are simple to implement, cost-effective, and frequently require only a simple domain name system (DNS) or proxy configuration update to reroute application traffic. Although it can be challenging to delegate responsibility for filtering an organisation’s web application traffic to a third-party provider, this strategy enables applications to be protected across a diverse range of hosting locations and employ similar policies to defend against application layer attacks. Additionally, these third parties have access to the most up-to-date threat intelligence, which enables them to assist in identifying and blocking the most recent application security risks.

How does it work?

WAF - Infinitive HostA WAF examines HTTP requests and applies a set of rules that specify which portions of the communication are benign and which are malicious. A WAF examines the GET and POST requests as the primary components of HTTP communications. POST requests are used to deliver data to a server in order to alter its state. GET requests are used to get data from the server. A WAF can analyse and filter the content included in these HTTP requests in one of two ways, or a mix of the two:

– Whitelisting: A whitelisting method means that the WAF will block all requests by default and will accept only known-to-be-trusted requests. It contains a list of known-safe IP addresses. Whitelisting consumes fewer resources than blacklisting. The disadvantage of a whitelisting strategy is that it may inadvertently block harmless traffic. While it throws a wide net and can be effective, it also has the potential to be inaccurate.

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– Blacklisting: A blacklisting strategy begins by allowing packets to pass and then employs predefined signatures to prevent harmful online traffic and safeguard websites or web apps from vulnerabilities. It is a collection of rules used to identify malicious packets. Blacklisting is more ideal for public websites and online apps, as they get a high volume of traffic from unknown IP addresses that are neither harmful nor benign. The disadvantage of a blacklisting strategy is that it consumes more resources; filtering packets based on specific characteristics requires more information than just defaulting to trustworthy IP addresses.

– A hybrid security model combines parts of blacklisting and whitelisting. Whatever security architecture a WAF employs, it is ultimately responsible for analysing HTTP interactions and reducing or, ideally, eliminating harmful traffic before it reaches a server for processing.


The worldwide web application firewall market is expanding, owing to the increasing acceptance of cloud-based web application firewall services. Gartner, an information technology consulting organisation, undertook significant data research to determine the WAF market’s trends, direction, maturity, and participants.

Enterprise security and information technology teams may utilise the Gartner study on web application firewalls as a reference for analysing, setting, and maintaining a WAF security architecture in order to deliver the best WAF solution for their unique needs.

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