GitHub Repo

Detection: Windows DLL Side-Loading In Calc

Updated Date: 2026-02-23 ID: af01f6db-26ac-440e-8d89-2793e303f137 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the loading of the "WindowsCodecs.dll" by calc.exe from a non-standard location This could be indicative of a potential DLL side-loading technique. This detection leverages Sysmon EventCode 7 to identify the DLL side-loading activity. In previous versions of the "calc.exe" binary, namely on Windows 7, it was vulnerable to DLL side-loading, where an attacker is able to load an arbitrary DLL named "WindowsCodecs.dll". This technique has been observed in Qakbot malware. This activity is significant as it indicates potential malware execution through a trusted process, which can bypass security controls. If confirmed malicious, this could allow attackers to execute arbitrary code, maintain persistence, and escalate privileges within the environment.

 1'`sysmon`
 2EventCode=7
 3Image="*\\calc.exe"
 4ImageLoaded="*\\WindowsCodecs.dll"
 5NOT Image IN ("*:\\Windows\\System32\\*", "*:\\Windows\\SysWOW64\\*")
 6NOT ImageLoaded IN("*:\\Windows\\System32\\*", "*:\\Windows\\SysWOW64\\*", "*:\\Windows\\WinSXS\\*")
 7
 8
 9| fillnull
10
11| stats count min(_time) as firstTime max(_time) as lastTime
12
13by Image ImageLoaded dest loaded_file loaded_file_path original_file_name
14   process_exec process_guid process_hash process_id process_name
15   process_path service_dll_signature_exists service_dll_signature_verified
16   signature signature_id user_id vendor_product
17
18
19| `security_content_ctime(firstTime)`
20
21| `security_content_ctime(lastTime)`
22
23| `windows_dll_side_loading_in_calc_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 7 Windows icon 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_dll_side_loading_in_calc_filter search *
windows_dll_side_loading_in_calc_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
T1574.001 DLL Defense Evasion
Exploitation
Installation
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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search you need to be ingesting information on processes that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes and Filesystem 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

Risk Based Analytics (RBA)

Risk Message:

The [ $Image$ ] process loaded the [ $ImageLoaded$ ] DLL from a non-standard location on [ $dest$ ]

Risk Object Risk Object Type Risk Score Threat Objects
dest system 90 No Threat Objects

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: 10