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 |
Detection: Exploit Public Facing Application via Apache Commons Text
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.
Search
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
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 |
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 notable) if removal of other_lookups occur and Score is raised to 2 (down from 4).
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A URL was requested related to Text4Shell on $dest$ by $src$. | 49 | 70 | 70 |
References
-
https://lists.apache.org/thread/n2bd4vdsgkqh2tm14l1wyc3jyol7s1om
-
https://www.rapid7.com/blog/post/2022/10/17/cve-2022-42889-keep-calm-and-stop-saying-4shell/
-
https://medium.com/geekculture/text4shell-exploit-walkthrough-ebc02a01f035
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: 4