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Description

The following analytic identifies attempts to inject Log4Shell JNDI payloads via web calls. It leverages the Web datamodel and uses regex to detect patterns like ${jndi:ldap:// in raw web event data, including HTTP headers. This activity is significant because it targets vulnerabilities in Java web applications using Log4j, such as Apache Struts and Solr. If confirmed malicious, this could allow attackers to execute arbitrary code, potentially leading to full system compromise. Immediate investigation is required to determine if the attempt was successful and to mitigate any potential exploitation.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Web
  • Last Updated: 2024-05-25
  • Author: Jose Hernandez
  • ID: c184f12e-5c90-11ec-bf1f-497c9a704a72

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1190 Exploit Public-Facing Application Initial Access
T1133 External Remote Services Persistence, Initial Access
Kill Chain Phase
  • Delivery
  • Installation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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| from datamodel Web.Web 
| regex _raw="[jJnNdDiI]{4}(\:
|\%3A
|\/
|\%2F)\w+(\:\/\/
|\%3A\%2F\%2F)(\$\{.*?\}(\.)?)?" 
| fillnull 
| stats count by action, category, dest, dest_port, http_content_type, http_method, http_referrer, http_user_agent, site, src, url, url_domain, user 
| `log4shell_jndi_payload_injection_attempt_filter`

Macros

The SPL above uses the following Macros:

:information_source: log4shell_jndi_payload_injection_attempt_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • action
  • category
  • dest
  • dest_port
  • http_content_type
  • http_method
  • http_referrer
  • http_user_agent
  • site
  • src
  • url
  • url_domain
  • user

How To Implement

This detection requires the Web datamodel to be populated from a supported Technology Add-On like Splunk for Apache or Splunk for Nginx.

Known False Positives

If there is a vulnerablility scannner looking for log4shells this will trigger, otherwise likely to have low false positives.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
15.0 50 30 CVE-2021-44228 Log4Shell triggered for host $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 2