Windows Anomalous Registry Value Length in Environment Key

name: Windows Anomalous Registry Value Length in Environment Key
id: f5bde743-245a-4e1f-a152-3971cec6e9ef
version: 2
creation_date: '2026-04-29'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: |-
    The following analytic detects creation or modification of registry values under a user or system Environment key (paths matching *\Environment\*) where the stored value exceeds 2,000 characters.
    Legitimate environment variables are typically short strings (paths, tokens, or flags); unusually long values can indicate adversaries or malware staging encoded payloads, bloated malicious PATH entries, or other data in a location that is loaded for every interactive session.
    This behavior has been observed in contexts such as .NET infostealer activity. Analysts should validate the writing process, value content, and whether the change aligns with trusted software deployment or administrative tasks.
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.action IN ("created", "modified")
    Registry.registry_path= "*\\Environment\\*"
    Registry.registry_value_name != "Path"

    by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive  Registry.registry_key_name  Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product Registry.registry_value_data Registry.registry_path
    | `drop_dm_object_name(Registry)`
    | eval registry_value_data_len = len(registry_value_data)
    | where registry_value_data_len > 2000
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_anomalous_registry_value_length_in_environment_key_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: No false positives have been identified at this time.
references:
    - https://www.joesandbox.com/analysis/1817558/0/pdfexecutive
    - https://www.broadcom.com/support/security-center/protection-bulletin/vip-keylogger-spreads-via-multi-org-impersonation-campaign
    - https://malpedia.caad.fkie.fraunhofer.de/details/win.vipkeylogger
drilldown_searches:
    - name: View the detection results for - "$dest$" and "$user$"
      search: '%original_detection_search% | search  dest = "$dest$" user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$" and "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: An anomalous registry value length of [$registry_value_data_len$] characters in [$registry_value_data$] was detected on [$dest$].
threat_objects:
    - field: registry_path
      type: registry_path
    - field: registry_value_data
      type: registry_value_text
analytic_story:
    - VIP Keylogger
asset_type: Endpoint
mitre_attack_id:
    - T1112
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1112/vip_big_env_variable/vip_INTERNAL_DB_CACHE.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit