This search is to detect a suspicious rundll32 process that drops executable (.exe or .dll) files. this behavior seen in rundll32 process of IcedID that tries to drop copy of itself in temp folder or download executable drop it either appdata or programdata as part of its execution.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-07-26
- Author: Teoderick Contreras, Splunk
- ID: 6338266a-ee2a-11eb-bf68-acde48001122
Kill Chain Phase
1 2 3 4 5 `sysmon` EventCode=11 process_name="rundll32.exe" TargetFilename IN ("*.exe", "*.dll",) | stats count min(_time) as firstTime max(_time) as lastTime by Image TargetFilename ProcessGuid dest user_id | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `rundll32_process_creating_exe_dll_files_filter`
The SPL above uses the following Macros:
rundll32_process_creating_exe_dll_files_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this search, you need to be ingesting logs with the process name, TargetFilename, and eventcode 11 executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where renamed rundll32.exe may be used.
Known False Positives
Associated Analytic Story
|80.0||80||100||rundll32 process $process_name$ drops a file $TargetFilename$ in host $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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