Detection: Rundll32 CreateRemoteThread In Browser

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2026-06-29 ID: f8a22586-ee2d-11eb-a193-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the suspicious creation of a remote thread by rundll32.exe targeting browser processes such as firefox.exe, chrome.exe, iexplore.exe, and microsoftedgecp.exe. This detection leverages Sysmon EventCode 8, focusing on SourceImage and TargetImage fields to identify the behavior. This activity is significant as it is commonly associated with malware like IcedID, which hooks browsers to steal sensitive information such as banking details. If confirmed malicious, this could allow attackers to intercept and exfiltrate sensitive user data, leading to potential financial loss and privacy breaches.

Search

 1`sysmon`
 2EventCode=8
 3SourceImage="*\\rundll32.exe"
 4TargetImage IN (
 5    "*\\chrome.exe",
 6    "*\\firefox.exe",
 7    "*\\iexplore.exe",
 8    "*\\microsoftedgecp.exe"
 9)
10
11| stats count min(_time) as firstTime
12              max(_time) as lastTime
13              values(NewThreadId) as "NewThreadId"
14              values(StartAddress) as "StartAddress"
15  by dest signature_id signature
16     SourceProcessGuid SourceProcessId SourceImage
17     TargetProcessGuid TargetProcessId TargetImage
18     StartModule StartFunction
19     SourceUser TargetUser vendor_product
20
21| `security_content_ctime(firstTime)`
22
23| `security_content_ctime(lastTime)`
24
25| `rundll32_createremotethread_in_browser_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 8	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
sysmon	`(source=WinEventLog:Microsoft-Windows-Sysmon/Operational OR source=XmlWinEventLog:Microsoft-Windows-Sysmon/Operational OR source=Syslog:Linux-Sysmon/Operational)`
rundll32_createremotethread_in_browser_filter	`search *`

rundll32_createremotethread_in_browser_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
T1055	Process Injection	Privilege Escalation

Exploitation

DE.CM

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

To successfully implement this search, you need to be ingesting logs with the SourceImage, TargetImage, and EventCode executions from your endpoints related to create remote thread or injecting codes. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

No false positives have been identified at this time.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
rundl32 process $SourceImage$ create a remote thread to browser process $TargetImage$ in host $dest$	dest	system	50

Threat Objects

Field	Type
SourceImage	process

References

https://www.joesandbox.com/analysis/380662/0/html

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	❌ Failing	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: 11