What is a Web Application Firewall (WAF)?  An explanation

By filtering and monitoring HTTP traffic between a web application and the Internet, a web application firewall, or WAF, contributes to the protection of online applications. It protects web applications from several kinds of attacks, such as cross-site scripting (XSS), file inclusion, SQL injection, and cross-site forgery.

A WAF is a protocol layer 7 protection in the OSI model. It is not intended to fight against all kinds of assaults. This attack mitigation technique is typically a component of a tool suite that works in concert to provide a comprehensive protection against a variety of attack vectors.

A web application and the Internet are shielded from one another by placing a WAF in front of it. A WAF is a sort of reverse-proxy that shields the server from exposure by requiring clients to pass through it before contacting the server, in contrast to a proxy server, which protects a client machine's identity by acting as an intermediary.

A WAF is governed by a set of guidelines known as policies. By removing harmful traffic, these rules try to guard against application vulnerabilities. Rate restriction during a DDoS assault may be promptly enforced by updating WAF policies, which adds value. The speed and ease with which policy modifications can be made allows for faster reaction to different attack vectors.

Known attacks are thwarted by a WAF that uses a blocklist (negative security paradigm) to function. Consider a blocklist WAF as a club bouncer with the authority to refuse entry to anybody not dressed appropriately. A WAF based on an allowlist, on the other hand, only allows traffic that has been pre-approved (positive security model).

Similar to the bouncer at a private party, this person only lets those on the list in. Because allowlists and blocklists each have benefits and downsides, many WAFs provide a hybrid security paradigm that combines the two.

There are three approaches to install a WAF, each with advantages and disadvantages of its own:

Hardware is often the foundation of a network-based WAF. Local installation reduces latency; nevertheless, network-based WAFs are the most costly solution and need the storage and upkeep of real equipment.

The software of an application may completely incorporate a host-based WAF. Compared to a network-based WAF, this solution is more affordable and customizable. The use of local server resources, implementation complexity, and maintenance expenses are the drawbacks of a host-based WAF. These parts can be expensive and usually need engineering effort.

Cloud-based WAFs provide an easy-to-use and reasonably priced solution; most provide a turnkey installation that just requires rerouting traffic through a DNS change. Due to the fact that customers pay monthly or yearly for security as a service, cloud-based WAFs also offer a low upfront cost.

Additionally, cloud-based WAFs can provide a solution that is automatically updated to defend against the most recent threats without requiring the user to perform any extra work or pay any extra fees. A cloud-based WAF has the disadvantage of transferring user accountability to a third party, which means that some functions may be hidden from users. (One kind of cloud firewall is a cloud-based WAF; find out more about cloud firewalls.)