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Description

The following analytic detects attempts to exploit the CVE-2022-42889 vulnerability in the Apache Commons Text Library, known as Text4Shell. It leverages the Web datamodel to identify suspicious HTTP requests containing specific lookup keys (url, dns, script) that can lead to Remote Code Execution (RCE). This activity is significant as it targets a critical vulnerability that can allow attackers to execute arbitrary code on the server. If confirmed malicious, this could lead to full system compromise, data exfiltration, or further lateral movement within the network.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Web
  • Last Updated: 2024-05-21
  • Author: Michael Haag, Splunk
  • ID: 19a481e0-c97c-4d14-b1db-75a708eb592e

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1505.003 Web Shell Persistence
T1505 Server Software Component Persistence
T1190 Exploit Public-Facing Application Initial Access
T1133 External Remote Services Persistence, Initial Access
Kill Chain Phase
  • Installation
  • Delivery
NIST
  • DE.AE
CIS20
  • CIS 13
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Web where Web.http_method IN (POST, GET) by Web.src Web.status Web.uri_path Web.dest Web.http_method Web.uri_query Web.http_user_agent 
| `drop_dm_object_name("Web")` 
| eval utf=if(like(lower(uri_query),"%:utf-8:http%"),2,0) 
| eval lookup = if(like(lower(uri_query), "%url%") OR like(lower(uri_query), "%dns%") OR like(lower(uri_query), "%script%"),2,0) 
| eval other_lookups = if(like(lower(uri_query), "%env%") OR like(lower(uri_query), "%file%") OR like(lower(uri_query), "%getRuntime%") OR like(lower(uri_query), "%java%") OR like(lower(uri_query), "%localhost%") OR like(lower(uri_query), "%properties%") OR like(lower(uri_query), "%resource%") OR like(lower(uri_query), "%sys%") OR like(lower(uri_query), "%xml%") OR like(lower(uri_query), "%base%"),1,0) 
| addtotals fieldname=Score utf lookup other_lookups 
| fields Score, src, dest, status, uri_query, uri_path, http_method, http_user_agent firstTime lastTime 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| where Score >= 3 
| `exploit_public_facing_application_via_apache_commons_text_filter`

Macros

The SPL above uses the following Macros:

:information_source: exploit_public_facing_application_via_apache_commons_text_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.

  • _time
  • Web.http_method
  • Web.src
  • Web.dest
  • Web.http_user_agent
  • Web.status
  • Web.uri_query
  • Web.uri_path

How To Implement

To implement, one must be collecting network traffic that is normalized in CIM and able to be queried via the Web datamodel. Or, take the chunks out needed and tie to a specific network source type to hunt in. Tune as needed, or remove the other_lookups statement.

Known False Positives

False positives are present when the values are set to 1 for utf and lookup. It's possible to raise this to TTP (direct notable) if removal of other_lookups occur and Score is raised to 2 (down from 4).

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
49.0 70 70 A URL was requested related to Text4Shell on $dest$ by $src$.

: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: 3