ID | Technique | Tactic |
---|---|---|
T1505.003 | Web Shell | Persistence |
T1133 | External Remote Services | Initial Access |
Detection: Supernova Webshell
EXPERIMENTAL DETECTION
This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.
Description
The following analytic detects the presence of the Supernova webshell, used in the SUNBURST attack, by identifying specific patterns in web URLs. The detection leverages Splunk to search for URLs containing "logoimagehandler.ashxcodes*", "logoimagehandler.ashxclazz*", "logoimagehandler.ashxmethod*", and "logoimagehandler.ashxargs*". This activity is significant as it indicates potential unauthorized access and arbitrary code execution on a compromised system. If confirmed malicious, this could lead to data theft, ransomware deployment, or other severe outcomes. Immediate steps include reviewing the web URLs, inspecting on-disk artifacts, and analyzing concurrent processes and network connections.
Search
1
2| tstats `security_content_summariesonly` count from datamodel=Web.Web where web.url=*logoimagehandler.ashx*codes* OR Web.url=*logoimagehandler.ashx*clazz* OR Web.url=*logoimagehandler.ashx*method* OR Web.url=*logoimagehandler.ashx*args* by Web.src Web.dest Web.url Web.vendor_product Web.user Web.http_user_agent _time span=1s
3| `supernova_webshell_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
security_content_summariesonly | summariesonly= summariesonly_config allow_old_summaries= oldsummaries_config fillnull_value= fillnull_config`` |
supernova_webshell_filter | search * |
supernova_webshell_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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
To successfully implement this search, you need to be monitoring web traffic to your Solarwinds Orion. The logs should be ingested into splunk and populating/mapped to the Web data model.
Known False Positives
There might be false positives associted with this detection since items like args as a web argument is pretty generic.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
tbd | 25 | 50 | 50 |
References
-
https://www.splunk.com/en_us/blog/security/detecting-supernova-malware-solarwinds-continued.html
-
https://www.guidepointsecurity.com/blog/supernova-solarwinds-net-webshell-analysis/
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | Not Applicable | N/A | N/A | N/A |
Unit | ❌ Failing | N/A | N/A |
N/A |
Integration | ❌ Failing | N/A | N/A |
N/A |
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: 2