Elastic low stable kql

Web Server Potential Command Injection Request

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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Detection Logic

from logs-nginx.access-*, logs-apache.access-*, logs-apache_tomcat.access-*, logs-iis.access-*, logs-traefik.access-*
| where
    // Limit to 200 response code to reduce noise
    http.response.status_code == 200
| eval Esql.url_original_to_lower = to_lower(url.original)
| eval Esql.contains_interpreter = case(Esql.url_original_to_lower like "*python* -c*" or Esql.url_original_to_lower like "*perl* -e*" or Esql.url_original_to_lower like "*ruby* -e*" or Esql.url_original_to_lower like "*ruby* -rsocket*" or Esql.url_original_to_lower like "*lua* -e*" or Esql.url_original_to_lower like "*php* -r*" or Esql.url_original_to_lower like "*node* -e*", 1, 0)
| eval Esql.contains_shell = case(Esql.url_original_to_lower like "*/bin/bash*" or Esql.url_original_to_lower like "*bash*-c*" or Esql.url_original_to_lower like "*/bin/sh*" or Esql.url_original_to_lower rlike "*sh.{1,2}-c*", 1, 0)
| eval Esql.contains_nc = case(Esql.url_original_to_lower like "*netcat*" or Esql.url_original_to_lower like "*ncat*" or Esql.url_original_to_lower rlike """.*nc.{1,2}[0-9]{1,3}(\.[0-9]{1,3}){3}.{1,2}[0-9]{1,5}.*""" or Esql.url_original_to_lower like "*nc.openbsd*" or Esql.url_original_to_lower like "*nc.traditional*" or Esql.url_original_to_lower like "*socat*", 1, 0)
| eval Esql.contains_devtcp = case(Esql.url_original_to_lower like "*/dev/tcp/*" or Esql.url_original_to_lower like "*/dev/udp/*", 1, 0)
| eval Esql.contains_helpers = case((Esql.url_original_to_lower like "*/bin/*" or Esql.url_original_to_lower like "*/usr/bin/*") and (Esql.url_original_to_lower like "*mkfifo*" or Esql.url_original_to_lower like "*nohup*" or Esql.url_original_to_lower like "*setsid*" or Esql.url_original_to_lower like "*busybox*"), 1, 0)
| eval Esql.contains_sus_cli = case(Esql.url_original_to_lower like "*import*pty*spawn*" or Esql.url_original_to_lower like "*import*subprocess*call*" or Esql.url_original_to_lower like "*tcpsocket.new*" or Esql.url_original_to_lower like "*tcpsocket.open*" or Esql.url_original_to_lower like "*io.popen*" or Esql.url_original_to_lower like "*os.execute*" or Esql.url_original_to_lower like "*fsockopen*", 1, 0)
| eval Esql.contains_privileges = case(Esql.url_original_to_lower like "*chmod*+x", 1, 0)
| eval Esql.contains_downloader = case(Esql.url_original_to_lower like "*curl *" or Esql.url_original_to_lower like "*wget *" , 1, 0)
| eval Esql.contains_file_read_keywords = case(Esql.url_original_to_lower like "*/etc/shadow*" or Esql.url_original_to_lower like "*/etc/passwd*" or Esql.url_original_to_lower like "*/root/.ssh/*" or Esql.url_original_to_lower like "*/home/*/.ssh/*" or Esql.url_original_to_lower like "*~/.ssh/*" or Esql.url_original_to_lower like "*/proc/self/environ*", 1, 0)
| eval Esql.contains_base64_cmd = case(Esql.url_original_to_lower like "*base64*-d*" or Esql.url_original_to_lower like "*echo*
| *base64*", 1, 0)
| eval Esql.contains_suspicious_path = case(Esql.url_original_to_lower like "*/tmp/*" or Esql.url_original_to_lower like "*/var/tmp/*" or Esql.url_original_to_lower like "*/dev/shm/*" or Esql.url_original_to_lower like "*/root/*" or Esql.url_original_to_lower like "*/home/*/*" or Esql.url_original_to_lower like "*/var/www/*" or Esql.url_original_to_lower like "*/etc/cron.*/*", 1, 0)
| eval Esql.any_payload_keyword = case(
    Esql.contains_interpreter == 1 or Esql.contains_shell == 1 or Esql.contains_nc == 1 or Esql.contains_devtcp == 1 or
    Esql.contains_helpers == 1 or Esql.contains_sus_cli == 1 or Esql.contains_privileges == 1 or Esql.contains_downloader == 1 or
    Esql.contains_file_read_keywords == 1 or Esql.contains_base64_cmd == 1 or Esql.contains_suspicious_path == 1, 1, 0)
| keep
    @timestamp,
    Esql.url_original_to_lower,
    Esql.any_payload_keyword,
    Esql.contains_interpreter,
    Esql.contains_shell,
    Esql.contains_nc,
    Esql.contains_devtcp,
    Esql.contains_helpers,
    Esql.contains_sus_cli,
    Esql.contains_privileges,
    Esql.contains_downloader,
    Esql.contains_file_read_keywords,
    Esql.contains_base64_cmd,
    Esql.contains_suspicious_path,
    source.ip,
    destination.ip,
    agent.id,
    http.request.method,
    http.response.status_code,
    user_agent.original,
    agent.name,
    data_stream.dataset,
    data_stream.namespace
| stats
    Esql.event_count = count(),
    Esql.url_path_count_distinct = count_distinct(Esql.url_original_to_lower),

    // General fields

    Esql.agent_name_values = values(agent.name),
    Esql.agent_id_values = values(agent.id),
    Esql.url_path_values = values(Esql.url_original_to_lower),
    Esql.http.response.status_code_values = values(http.response.status_code),
    Esql.user_agent_original_values = values(user_agent.original),
    Esql.data_stream_dataset_values = values(data_stream.dataset),
    Esql.data_stream_namespace_values = values(data_stream.namespace),

    // Rule Specific fields
    Esql.any_payload_keyword_max = max(Esql.any_payload_keyword),
    Esql.contains_interpreter_values = values(Esql.contains_interpreter),
    Esql.contains_shell_values = values(Esql.contains_shell),
    Esql.contains_nc_values = values(Esql.contains_nc),
    Esql.contains_devtcp_values = values(Esql.contains_devtcp),
    Esql.contains_helpers_values = values(Esql.contains_helpers),
    Esql.contains_sus_cli_values = values(Esql.contains_sus_cli),
    Esql.contains_privileges_values = values(Esql.contains_privileges),
    Esql.contains_downloader_values = values(Esql.contains_downloader),
    Esql.contains_file_read_keywords_values = values(Esql.contains_file_read_keywords),
    Esql.contains_base64_cmd_values = values(Esql.contains_base64_cmd),
    Esql.contains_suspicious_path_values = values(Esql.contains_suspicious_path)

    by source.ip, agent.id
| where
    // Filter for potential command injection attempts with low event counts to reduce false positives
    Esql.any_payload_keyword_max == 1 and Esql.event_count < 5

Field Validations

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