HTTP Request Smuggling

• HTTP Scripting Tool User Agent :
  network Network None version:6
  This Splunk query analyzes web access logs to identify and categorize non-browser user agents, detecting various types of security tools, scripting languages, automation frameworks, and suspicious patterns. This activity can signify malicious actors attempting to interact with web endpoints in non-standard ways.


• HTTP Duplicated Header :
  network Network None version:5
  Detects when a request has more than one of the same header. This is commonly used in request smuggling and other web based attacks. HTTP Request Smuggling exploits inconsistencies in how front-end and back-end servers parse HTTP requests by using ambiguous or malformed headers to hide malicious requests within legitimate ones. Attackers leverage duplicate headers, particularly Content-Length and Transfer-Encoding, to cause different servers in the chain to disagree on where one request ends and another begins. RFC7230 states that a sender MUST NOT generate multiple header fields with the same field name in a message unless either the entire field value for that header field is defined as a comma-separated list or the header field is a well-known exception.


• HTTP Suspicious Tool User Agent :
  network Network 2025-10-09 version:2
  This Splunk query analyzes web access logs to identify and categorize non-browser user agents, detecting various types of security tools, scripting languages, automation frameworks, and suspicious patterns. This activity can signify malicious actors attempting to interact with web endpoints in non-standard ways.


• HTTP Request to Reserved Name on IIS Server :
  network Network None version:6
  Detects attempts to exploit a request smuggling technique against IIS that leverages a Windows quirk where requests for reserved Windows device names such as "/con" trigger an early server response before the request body is received. When combined with a Content-Length desynchronization, this behavior can lead to a parsing confusion between frontend and backend.


• HTTP Possible Request Smuggling :
  network Network None version:5
  HTTP request smuggling is a technique for interfering with the way a web site processes sequences of HTTP requests that are received from one or more users. Request smuggling vulnerabilities are often critical in nature, allowing an attacker to bypass security controls, gain unauthorized access to sensitive data, and directly compromise other application users. This detection identifies a common request smuggling technique of using both Content-Length and Transfer-Encoding headers to cause a parsing confusion between the frontend and backend.


• HTTP Rapid POST with Mixed Status Codes :
  network Web Server None version:5
  This detection identifies rapid-fire POST request attacks where an attacker sends more than 20 POST requests within a 5-second window, potentially attempting to exploit race conditions or overwhelm request handling. The pattern is particularly suspicious when responses vary in size or status codes, indicating successful exploitation attempts or probing for vulnerable endpoints.