A web application firewall (WAF) is a type of firewall that is designed to protect web applications from various types of attacks. A WAF typically sits between the web application and the internet, and examines all incoming traffic to the application, blocking any traffic that appears to be malicious.
WAFs can be deployed either as a hardware appliance or as a software application. They can be used to protect against a wide range of attacks, including SQL injection, cross-site scripting (XSS), and cross-site request forgery (CSRF).
WAFs work by examining the traffic that is coming into the web application and comparing it to a set of predefined rules. If the traffic matches any of these rules, the WAF will block it. This can include blocking traffic from specific IP addresses, blocking traffic that contains certain keywords, or blocking traffic that looks suspicious in some other way.
Some WAFs are designed to be self-learning, meaning that they can adapt to new threats over time. They can also be configured to send alerts to security personnel when an attack is detected, allowing them to investigate and take appropriate action.
Overall, a WAF is an important tool in the fight against web application attacks and can help to protect sensitive data and prevent damage to web applications.