This detection rule identifies unusual spikes in error logs from web servers, which can indicate reconnaissance activities like vulnerability scanning or fuzzing attempts by attackers. Such activities lead to a high volume of error responses as adversaries attempt to find weaknesses in web applications. The rule focuses on capturing patterns of error responses that suggest probing actions, tracking spikes in HTTP error codes (e.g., 404, 403, 500) across various web server platforms including Nginx, Apache, Apache Tomcat, and IIS. Typical reconnaissance behaviors may include scanning for sensitive files or directories such as /.env, /.git, or access points like /admin/, generating bursts of error reports. The rule emphasizes on aggregating data by client IP, analyzing the request patterns, and performing follow-on checks for any successful access to sensitive endpoints after the detected spikes. It provides additional guidance on investigation steps, potential false positives, and effective remediation strategies to enhance the security posture.