Detection: Web or Application Server Spawning a Shell

Description

The following analytic detects instances where Java, or Tomcat processes spawn a Linux shell, which may indicate exploitation attempts, such as those related to CVE-2021-44228 (Log4Shell). This detection leverages Endpoint Detection and Response (EDR) telemetry, focusing on process names and parent-child process relationships. This activity is significant as it can signify a compromised Java application, potentially leading to unauthorized shell access. If confirmed malicious, attackers could execute arbitrary commands, escalate privileges, or maintain persistent access, posing a severe threat to the environment.

Search

 1
 2| tstats `security_content_summariesonly` 
 3  count min(_time) as firstTime 
 4        max(_time) as lastTime 
 5
 6from datamodel=Endpoint.Processes where 
 7
 8(
 9  Processes.parent_process_name IN ("java", "tomcat", "httpd", "lighttpd", "apache2", "nginx", "node", "caddy")
10  `linux_shells`
11)
12OR
13(
14  Processes.parent_process_name IN ("httpd.exe", "nginx.exe", "php.exe", "php-cgi.exe", "tomcat*.exe", "caddy.exe", "UMWorkerProcess.exe", "w3wp.exe", "ws_TomcatService.exe", "node.exe", "java.exe")
15  `windows_shells`
16)
17
18by Processes.action Processes.dest Processes.original_file_name Processes.parent_process
19   Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id
20   Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec
21   Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level 
22   Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product
23
24
25| `drop_dm_object_name(Processes)` 
26
27| `security_content_ctime(firstTime)` 
28
29| `security_content_ctime(lastTime)`
30
31| `web_or_application_server_spawning_a_shell_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon for Linux EventID 1	Linux	'sysmon:linux'	'Syslog:Linux-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

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

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Filtering may be required on internal developer build systems or classify assets as web facing and restrict the analytic based on asset type.

Associated Analytic Story

• Data Destruction

• Hermetic Wiper

• Log4Shell CVE-2021-44228

• Spring4Shell CVE-2022-22965

Risk Based Analytics (RBA)

Risk Message:

An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ spawning a Linux shell, potentially indicative of exploitation.

References

• https://blog.netlab.360.com/ten-families-of-malicious-samples-are-spreading-using-the-log4j2-vulnerability-now/

• https://gist.github.com/olafhartong/916ebc673ba066537740164f7e7e1d72

Detection Testing

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: 1