The Web Application Firewall or WAF is responsible for filtering, monitoring and blocking HTTP web traffic going to and coming from web applications. It is distinct from a standard firewall because the WAF is designed to filter content in specific web apps while the regular firewalls will work like safety gates in between servers. Since it inspects HTTP traffic, it is able to ward off attacks which may arise because of security flaws in different web applications. Some of these commonly occurring attacks are the XSS attacks or cross-scripting attacks, DDoS attacks, SQL injection attacks etc.
How the WAF will work:
The WAF will scan the web traffic to detect suspicious and malicious activities. It then filters out the illegitimate traffic depending upon the rules you have specifically set down. It will address both POST and GET requests and then apply rule sets which will cover the various vulnerabilities and help you understand which traffic to block, which traffic to challenge and which traffic you can allow to pass. So, it will be able to block cross-scripting attacks and SQL injection attacks successfully. The WAFs are very common security tools being used by enterprises today for protecting their web apps from zero-day exploits. You can even deploy customized inspections which will allow the WAFs to detect and stop XSS attacks and SQL injection attacks, buffer overflows, session hijacking etc that other standard firewalls cannot successfully prevent.
The network-based WAF is typically hardware-based and it can lower the latency as it is locally installed and near the application. Majority of the network-based web application firewall vendors will allow rules replication across many devices and makes large scale configurations possible. But, the key drawback of such a system is the huge costs. On the other hand, the application based web application firewall will guarantee low costs of deployment and better customizability. The cloud-hosted WAFs are also very cost-effective for businesses which look for turnkey products. They are also easier to deploy and can be obtained on subscription basis.