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Cloud Hosting Glossary

Struggling to tell your APIs from your CDNs? Read our comprehensive cloud computing glossary covering the most common terms.

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Web Application Firewall (WAF)

A Web Application Firewall (WAF) is a security appliance used to monitor, filter, and block HTTP traffic between a web application and the Internet. It performs as a reverse proxy to safeguard web applications against different attacks including SQL injection, cross-site scripting (XSS), and file inclusion by examining traffic on the application level.

How WAFs Work

Traffic Inspection: WAFs monitor incoming and outgoing HTTP traffic in order to detect and block malicious requests.

Rule-Based Policies: They work based on pre-defined policies or rules that determine what traffic to allow or deny. These can be rapidly updated to address new threats.

Deployment Options: WAFs may be implemented as network-based, host-based, or cloud-based solutions, providing flexibility in deployment.

Types of WAFs

Blocklist (Negative Security Model): Denies known malicious traffic based on pre-defined rules.

Allowlist (Positive Security Model): Only permits traffic that conforms to pre-defined safe conditions.

Hybrid Model: Synthesizes both blocklist and allowlist concepts for a more complete approach to security.

Advantages of WAFs

Defense from Known and Zero-Day Threats: Protects from typical web application weaknesses as well as unknown attacks.

Regulation Compliance: Allows organizations to fulfill security compliances such as PCI DSS through the secure handling of confidential data.

Agility and Expandability: Updated very easily in response to fresh threats and accommodate cloud-based instances easily.

Practical Example

Take, for instance, an e-commerce website that employs a WAF against SQL injection attacks. By putting a WAF in front of the web app, the site can block malicious traffic, thereby keeping sensitive customer information safe and preventing potential hacks.

Things to Keep in Mind

Configuration and Updates: Continuously check and update WAF policies to maintain effectiveness against continually changing threats.

Integration with Other Security Solutions: Integrate WAFs with other security products such as intrusion detection systems for complete protection.

Performance Impact: Keep a check on the performance impact of WAFs so that they do not cause excessive latency or overhead.