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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This rule detects unusual spikes in error logs from web servers, which may indicate reconnaissance activities such as vulnerability scanning or fuzzing attempts by adversaries. These activities often generate a high volume of error responses as they probe for weaknesses in web applications. Error response codes may potentially indicate server-side issues that could be exploited.

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This rule detects potential web server discovery or fuzzing activity by identifying a high volume of HTTP GET requests resulting in 404 or 403 status codes from a single source IP address within a short timeframe. Such patterns may indicate that an attacker is attempting to discover hidden or unlinked resources on a web server, which can be a precursor to more targeted attacks.

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This rule detects potential command injection attempts via web server requests by identifying URLs that contain suspicious patterns commonly associated with command execution payloads. Attackers may exploit vulnerabilities in web applications to inject and execute arbitrary commands on the server, often using interpreters like Python, Perl, Ruby, PHP, or shell commands. By monitoring for these indicators in web traffic, security teams can identify and respond to potential threats early.

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This rule detects unusual spikes in error response codes (500, 502, 503, 504) from web servers, which may indicate reconnaissance activities such as vulnerability scanning or fuzzing attempts by adversaries. These activities often generate a high volume of error responses as they probe for weaknesses in web applications. Error response codes may potentially indicate server-side issues that could be exploited.

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This rule detects unusual spikes in web server requests with uncommon or suspicious user-agent strings. Such activity may indicate reconnaissance attempts by attackers trying to identify vulnerabilities in web applications or servers. These user-agents are often associated with automated tools used for scanning, vulnerability assessment, or brute-force attacks.

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