Unusual File Creation by Web Server

This rule detects unusual file creations from a web server parent process. Adversaries may attempt to create files from a web server parent process to establish persistence, execute malicious scripts, or exfiltrate data. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.

Rule type: esql
Rule indices:

Rule Severity: medium
Risk Score: 47
Runs every: 1h
Searches indices from: now-61m
Maximum alerts per execution: ?
References:

Tags:

• Domain: Endpoint
• OS: Linux
• Use Case: Threat Detection
• Tactic: Persistence
• Tactic: Execution
• Tactic: Command and Control
• Data Source: Elastic Defend
• Rule Type: BBR

Version: ?
Rule authors:

• Elastic

Rule license: Elastic License v2

This rule requires data coming in from Elastic Defend.

Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.

• Fleet is required for Elastic Defend.
• To configure Fleet Server refer to the documentation.

• Go to the Kibana home page and click "Add integrations".
• In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
• Click "Add Elastic Defend".
• Configure the integration name and optionally add a description.
• Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
• Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. Helper guide.
• We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
• Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead. For more details on Elastic Agent configuration settings, refer to the helper guide.
• Click "Save and Continue".
• To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts. For more details on Elastic Defend refer to the helper guide.

from logs-endpoint.events.file-*
| keep @timestamp, host.os.type, event.type, event.action, user.name, user.id, process.name, process.executable, file.path, agent.id, host.name
| where @timestamp > now() - 1 hours
| where host.os.type == "linux" and event.type == "change" and event.action in ("rename", "creation") and (
     user.name in (
      "apache", "www-data", "httpd", "nginx", "lighttpd", "tomcat", "tomcat8", "tomcat9", "ftp", "ftpuser", "ftpd"
     ) or
     user.id in ("99", "33", "498", "48")
   ) and (
   process.name in (
    "apache", "nginx", "apache2", "httpd", "lighttpd", "caddy", "node", "mongrel_rails", "java", "gunicorn",
    "uwsgi", "openresty", "cherokee", "h2o", "resin", "puma", "unicorn", "traefik", "tornado", "hypercorn",
    "daphne", "twistd", "yaws", "webfsd", "httpd.worker", "flask", "rails", "mongrel"
  ) or
    process.name like "php-*" or
    process.name like "python*" or
    process.name like "ruby*" or
    process.name like "perl*"
   )
| stats cc = count(), agent_count = count_distinct(agent.id), host.name = VALUES(host.name), agent.id = VALUES(agent.id) by process.executable, file.path
| where agent_count == 1 and cc < 5
| sort cc asc
| limit 100

Framework: MITRE ATT&CK

• Tactic:

  • Name: Persistence
  • Id: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Server Software Component
  • Id: T1505
  • Reference URL: https://attack.mitre.org/techniques/T1505/

• Sub Technique:

  • Name: Web Shell
  • Id: T1505.003
  • Reference URL: https://attack.mitre.org/techniques/T1505/003/

Framework: MITRE ATT&CK

• Tactic:

  • Name: Execution
  • Id: TA0002
  • Reference URL: https://attack.mitre.org/tactics/TA0002/

• Technique:

  • Name: Command and Scripting Interpreter
  • Id: T1059
  • Reference URL: https://attack.mitre.org/techniques/T1059/

• Sub Technique:

  • Name: Unix Shell
  • Id: T1059.004
  • Reference URL: https://attack.mitre.org/techniques/T1059/004/

Framework: MITRE ATT&CK

• Tactic:

  • Name: Command and Control
  • Id: TA0011
  • Reference URL: https://attack.mitre.org/tactics/TA0011/

• Technique:

  • Name: Application Layer Protocol
  • Id: T1071
  • Reference URL: https://attack.mitre.org/techniques/T1071/