schcache_change_by_app_connect_and_create_adsi_object.yml

name: SchCache Change By App Connect And Create ADSI Object
id: 991eb510-0fc6-11ec-82d3-acde48001122
version: 1
date: '2021-09-07'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: This analytic is to detect an application try to connect and create ADSI
  Object to do LDAP query. Every time an application connects to the directory and
  attempts to create an ADSI object, the Active Directory Schema is checked for changes.
  If it has changed since the last connection, the schema is downloaded and stored
  in a cache on the local computer either in %LOCALAPPDATA%\Microsoft\Windows\SchCache
  or %systemroot%\SchCache. We found this a good anomaly use case to detect suspicious
  application like blackmatter ransomware that use ADS object api to execute ldap
  query. having a good list of ldap or normal AD query tool used within the network
  is a good start to reduce the noise.
data_source:
- Sysmon EventID 11
search: '`sysmon` EventCode=11  TargetFilename = "*\\Windows\\SchCache\\*" TargetFilename
  = "*.sch*" NOT (Image IN ("*\\Windows\\system32\\mmc.exe")) |stats count min(_time)
  as firstTime max(_time) as lastTime by Image TargetFilename EventCode process_id  process_name
  dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
  | `schcache_change_by_app_connect_and_create_adsi_object_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the process name, parent process, and command-line executions from your
  endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the
  Sysmon TA.
known_false_positives: normal application like mmc.exe and other ldap query tool may
  trigger this detections.
references:
- https://docs.microsoft.com/en-us/windows/win32/adsi/adsi-and-uac
- https://news.sophos.com/en-us/2021/08/09/blackmatter-ransomware-emerges-from-the-shadow-of-darkside/
tags:
  analytic_story:
  - BlackMatter Ransomware
  asset_type: Endpoint
  confidence: 50
  impact: 50
  message: process $Image$ create a file $TargetFilename$ in host $dest$
  mitre_attack_id:
  - T1087.002
  - T1087
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Image
  - TargetFilename
  - EventCode
  - process_id
  - process_name
  - dest
  risk_score: 25
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1087.002/blackmatter_schcache/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog