Web scanning is a reconnaissance technique used by both security professionals and malicious actors to discover vulnerabilities in web applications and servers. Understanding how these scans work is essential for defending your infrastructure against potential attacks.

Attackers typically begin with port scanning to identify open services on a target system. Tools like Nmap can quickly determine which ports are listening and what services are running. Once web services are identified on ports 80 or 443, more specialized scanning begins to enumerate the application attack surface.

Directory brute forcing is a common next step where scanners attempt to discover hidden files and directories by trying common paths like /admin, /backup, /.git, and /wp-admin. Each 404 response narrows down what does not exist, while 200 or 403 responses reveal potentially interesting targets worth further investigation.

Vulnerability scanners then probe discovered endpoints for known weaknesses. These tools check for outdated software versions, misconfigurations, SQL injection points, cross-site scripting vulnerabilities, and other common security flaws. Automated scanners can test thousands of potential vulnerabilities in minutes.

Defending against web scanning requires multiple strategies. Web application firewalls can detect and block suspicious scanning patterns. Rate limiting prevents rapid enumeration attempts. Security headers like X-Frame-Options and Content-Security-Policy harden the application layer. Regular vulnerability assessments using the same tools attackers employ help identify weaknesses before they can be exploited.