What is the primary tool used for filtering or blocking malicious content on a network edge?

The primary tool used for filtering or blocking malicious content on a network edge is a Web Application Firewall (WAF). A WAF is specifically designed to monitor, filter, and protect HTTP traffic to and from a web application. It operates at the application layer and is capable of detecting and mitigating various types of attacks, such as cross-site scripting (XSS), SQL injection, and other application layer vulnerabilities. By analyzing incoming and outgoing traffic against predefined security rules, a WAF helps ensure that potentially harmful requests are blocked before they can affect the web application.

The other options serve different purposes and are not primarily focused on filtering or blocking malicious content at the network edge. Forensic Explorer is a digital forensics tool used to analyze and recover data from various media sources. OSSIM (Open Source Security Information Management) is a security management solution that combines multiple security tools for comprehensive monitoring and incident detection but does not specifically function as a content filtering tool at the network edge. Buck-Security does not refer to a widely recognized tool in this context and likely serves a different or limited function. Thus, the WAF is the most effective and appropriate tool for the task at hand.