Detection: Windows Anomalous Registry Value Length in Environment Key

Updated Date: 2026-04-16 ID: f5bde743-245a-4e1f-a152-3971cec6e9ef Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6FROM datamodel=Endpoint.Registry WHERE
 7
 8Registry.action IN ("created", "modified")
 9Registry.registry_path= "*\\Environment\\*"
10Registry.registry_value_name != "Path"
11
12by 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
13
14| `drop_dm_object_name(Registry)`
15
16| eval registry_value_data_len = len(registry_value_data)
17
18| where registry_value_data_len > 2000
19
20| `security_content_ctime(firstTime)`
21
22| `security_content_ctime(lastTime)`
23
24| `windows_anomalous_registry_value_length_in_environment_key_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 13	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_anomalous_registry_value_length_in_environment_key_filter	`search *`

windows_anomalous_registry_value_length_in_environment_key_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1112	Modify Registry	Defense Impairment

Exploitation

Installation

DE.AE

CIS 10

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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.

Associated Analytic Story

VIP Keylogger

Risk Based Analytics (RBA)

Risk Message:

An anomalous registry value length of [$registry_value_data_len$] characters in [$registry_value_data$] was detected on [$dest$].

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	20	registry_path, registry_value_data

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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: 1