This rule detects potential initial access activity where an adversary uploads a web shell or malicious script to a web server via a file upload mechanism (e.g., through a web form using multipart/form-data), followed by a GET or POST request to access the uploaded file. By checking the body content of HTTP requests for file upload indicators such as "Content-Disposition: form-data" and "filename=", the rule identifies suspicious upload activities. This sequence of actions is commonly used by attackers to gain and maintain access to compromised web servers.

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Identifies successful exploitation of CVE-2023-50164, a critical path traversal vulnerability in Apache Struts 2 file upload functionality. This high-fidelity rule detects a specific attack sequence where a malicious multipart/form-data POST request with WebKitFormBoundary is made to a Struts .action upload endpoint, immediately followed by the creation of a JSP web shell file by a Java process in Tomcat's webapps directories. This correlated activity indicates active exploitation resulting in remote code execution capability through unauthorized file upload and web shell deployment.

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