Which AWS service is characterized as a web application firewall?

AWS WAF, which stands for AWS Web Application Firewall, is a service specifically designed to protect web applications from common web exploits that may affect application availability, compromise security, or consume excessive resources. It allows users to create rules to filter out malicious HTTP/S requests based on specified criteria, such as IP addresses, HTTP headers, HTTP body, URI strings, and more.

This targeted approach helps safeguard applications from various threats, including cross-site scripting (XSS) attacks and SQL injection, ensuring that legitimate traffic can perform as intended while malicious traffic is blocked. AWS WAF can also integrate with other AWS services like Amazon CloudFront and Application Load Balancer, enhancing its usability in various deployment architectures.

The other options refer to different functionalities. AWS Resource Access Manager is designed to share resources across accounts; AWS Network Firewall focuses on network-level protections and filtering; and AWS Directory Service is used for managing directories within AWS environments. None of these services serve the specific role that AWS WAF fulfills in application security.