What is a cloud web application firewall (WAF)?

A cloud web application firewall (or WAF) is a security service that protects web applications that are hosted in the cloud from malicious traffic.  Unlike traditional firewalls that are usually on-premises, a separate provider host and maintains the cloud WAF, and takes care of updates, availability, and development. It operates at  Layer 7 of the OSI (Open Systems Interconnection) model. Layer 7 is where end-user applications and services interact with each other over the internet, which is therefore the highest layer of network communication. Lower layers filter based on IP addresses, ports, or packet patterns, but a Layer 7 WAF can actually understand and inspect the content of web traffic. This tracks, because its main job - to inspect incoming HTTP/S requests and block threats.

These threats can be anything, including SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), and bot attacks, which are all application-level attacks. Modern cloud WAFs of today also leverage machine learning, threat intelligence, and behavioral analysis to detect and stop suspicious traffic by first identifying patterns (if any).

For example, if multiple failed login attempts come from a suspicious IP, the WAF can block the IP immediately while allowing legitimate users to proceed. Talking about the benefits of a cloud WAF, there are many. A cloud WAF can be deployed more quickly across multi-cloud environments, compliance is simplified (PCI-DSS, HIPAA, GDPR), and there's also scalability. Enterprises can protect against traffic surges without extra hardware. Therefore, any business that delivers its services online, a cloud WAF is a cost-effective and necessary security shield.