name: Supernova Webshell
id: 2ec08a09-9ff1-4dac-b59f-1efd57972ec1
version: 1
date: '2021-01-06'
author: John Stoner, Splunk
status: experimental
type: TTP
description: |-
  The following analytic detects the presence of the Supernova webshell, which was used in the SUNBURST attack. This webshell can be used by attackers to gain unauthorized access to a compromised system and run arbitrary code. This detection is made by a Splunk query that searches for specific patterns in web URLs, including "*logoimagehandler.ashx*codes*", "*logoimagehandler.ashx*clazz*", "*logoimagehandler.ashx*method*", and "*logoimagehandler.ashx*args*". These patterns are commonly used by the Supernova webshell to communicate with its command and control server. This detection is important because it indicates a potential compromise and unauthorized access to the system to run arbitrary code, which can lead to data theft, ransomware, or other damaging outcomes. False positives might occur since the patterns used by the webshell can also be present in legitimate web traffic. In such cases, tune the search to the specific environment and monitor it closely for any suspicious activity. Next steps include reviewing the web URLs and inspecting any relevant on-disk artifacts. Additionally, review concurrent processes and network connections to identify the source of the attack.
data_source: []
search: '| 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
  | `supernova_webshell_filter`'
how_to_implement: 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.
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/
tags:
  analytic_story:
  - NOBELIUM Group
  asset_type: Web Server
  confidence: 50
  impact: 50
  message: tbd
  mitre_attack_id:
  - T1505.003
  - T1133
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Web.url
  - Web.src
  - Web.dest
  - Web.vendor_product
  - Web.user
  - Web.http_user_agent
  risk_score: 25
  security_domain: network