How Attackers Use HTTP Status Codes for Malicious Purposes

HTTP status codes, which are three-digit numbers, communicate the outcome of client-server interactions and are categorized into informational, successful, redirection, client error, and server error responses. While these codes serve to inform users about the success or failure of their requests, they also present opportunities for attackers to exploit vulnerabilities within backend applications. Attackers can use these codes to map out server routes, identify potential flaws, and refine their attack strategies, particularly through automated tools that monitor status code changes. Although some suggest deliberately returning incorrect HTTP status codes to confuse attackers, this approach complicates debugging and does not address underlying security vulnerabilities, making adherence to API security best practices the preferred solution. Additionally, the guide emphasizes the importance of understanding how attackers leverage specific status codes, such as 200 OK, 400 Bad Request, 401 Unauthorized, 403 Forbidden, and others, to bypass security measures and suggests resources for improving web application security.