Windows Phishing Recent ISO Exec Registry

Name:Windows Phishing Recent ISO Exec Registry
id:cb38ee66-8ae5-47de-bd66-231c7bbc0b2c
version:7
date:2025-02-10
author:Teoderick Contreras, Splunk
status:production
type:Hunting
Description:The following analytic detects the creation of registry artifacts when an ISO container is opened, clicked, or mounted on a Windows operating system. It leverages data from the Endpoint.Registry data model, specifically monitoring registry keys related to recent ISO or IMG file executions. This activity is significant as adversaries increasingly use container-based phishing campaigns to bypass macro-based document execution controls. If confirmed malicious, this behavior could indicate an initial access attempt, potentially leading to further exploitation, persistence, or data exfiltration within the environment.
Data_source:

• -Sysmon EventID 13

search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry where Registry.registry_key_name= "*\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\RecentDocs\\.iso" OR Registry.registry_key_name= "*\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\RecentDocs\\.img" by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product
| `drop_dm_object_name(Registry)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_phishing_recent_iso_exec_registry_filter`

how_to_implement:To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Registry` node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.
known_false_positives:False positives may be high depending on the environment and consistent use of ISOs. Restrict to servers, or filter out based on commonly used ISO names. Filter as needed.
References:
  -https://www.microsoft.com/security/blog/2021/05/27/new-sophisticated-email-based-attack-from-nobelium/
  -https://unit42.paloaltonetworks.com/brute-ratel-c4-tool/
  -https://isc.sans.edu/diary/Recent+AZORult+activity/25120
  -https://tccontre.blogspot.com/2020/01/remcos-rat-evading-windows-defender-av.html
drilldown_searches:
  :
tags:
  analytic_story:
    - 'Brute Ratel C4'
    - 'AgentTesla'
    - 'Qakbot'
    - 'IcedID'
    - 'Azorult'
    - 'Remcos'
    - 'Warzone RAT'
    - 'Gozi Malware'
  asset_type:Endpoint
  mitre_attack_id:
    - 'T1566.001'
  product:
    - 'Splunk Enterprise'
    - 'Splunk Enterprise Security'
    - 'Splunk Cloud'
  security_domain:endpoint

tests:
 name:'True Positive Test'
 attack_data:
  data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/brute_ratel/iso_version_dll_campaign/sysmon.log
  source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
  sourcetype: XmlWinEventLog
manual_test:None