What type of attack does Server-Side Request Forgery (SSRF) involve?

Server-Side Request Forgery (SSRF) is primarily characterized by a server making unauthorized requests to internal or external resources. This type of attack occurs when an attacker exploits a vulnerable server to send requests on behalf of the server itself, often targeting internal systems that would otherwise be inaccessible. By crafting a request that the server processes, attackers can gain access to sensitive data or services that are meant to be hidden from external users, essentially leveraging the server's capabilities to interact with other systems.

In this context, the attack highlights the issues of improperly validated input and a server's trust in its own requests, which can lead to significant security vulnerabilities. Since the server does not distinguish between legitimate and malicious requests initiated from within its own environment, it can inadvertently expose itself and potentially sensitive internal systems to various threats. This behavior embodies the core aspects of SSRF.