Detection: Exploit Public Facing Application via Apache Commons Text

Updated Date: 2024-11-15 ID: 19a481e0-c97c-4d14-b1db-75a708eb592e Author: Michael Haag, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

 1
 2| 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 
 3| `drop_dm_object_name("Web")` 
 4| eval utf=if(like(lower(uri_query),"%:utf-8:http%"),2,0) 
 5| eval lookup = if(like(lower(uri_query), "%url%") OR like(lower(uri_query), "%dns%") OR like(lower(uri_query), "%script%"),2,0) 
 6| 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) 
 7| addtotals fieldname=Score utf lookup other_lookups 
 8| fields Score, src, dest, status, uri_query, uri_path, http_method, http_user_agent firstTime lastTime 
 9| `security_content_ctime(firstTime)` 
10| `security_content_ctime(lastTime)` 
11| where Score >= 3 
12| `exploit_public_facing_application_via_apache_commons_text_filter`

Data Source

Name Platform Sourcetype Source
Nginx Access N/A 'nginx:plus:kv' '/var/log/nginx/access.log'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
exploit_public_facing_application_via_apache_commons_text_filter search *
exploit_public_facing_application_via_apache_commons_text_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1505.003 Web Shell Persistence
T1505 Server Software Component Persistence
T1190 Exploit Public-Facing Application Initial Access
T1133 External Remote Services Initial Access
Delivery
Installation
DE.AE
CIS 13

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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 finding) if removal of other_lookups occur and Score is raised to 2 (down from 4).

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

A URL was requested related to Text4Shell on $dest$ by $src$.

Risk Object Risk Object Type Risk Score Threat Objects
dest system 49 src

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset nginx:plus:kv nginx:plus:kv
Integration ✅ Passing Dataset nginx:plus:kv nginx:plus:kv

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: GitHub | Version: 5