this search detects a potential malicious office document that create schedule task entry through macro VBA api or through loading taskschd.dll. This technique was seen in so many malicious macro malware that create persistence , beaconing using task schedule malware entry The search will return the first time and last time the task was registered, as well as the
Command to be executed,
Enabled, and whether it is
Hidden or not. schtasks.exe is natively found in
C:\Windows\syswow64. The following DLL(s) are loaded when schtasks.exe or TaskService is launched -
taskschd.dll. If found loaded by another process, it's possible a scheduled task is being registered within that process context in memory. Upon triage, identify the task scheduled source. Was it schtasks.exe or via TaskService? Review the job created and the Command to be executed. Capture any artifacts on disk and review. Identify any parallel processes within the same timeframe to identify source.'
- Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2023-02-15
- Author: Teoderick Contreras, Splunk
- ID: cc8b7b74-9d0f-11eb-8342-acde48001122
Kill Chain Phase
- CIS 10
1 2 3 4 5 6 `sysmon` EventCode=7 parent_process_name IN ("WINWORD.EXE", "EXCEL.EXE", "POWERPNT.EXE","onenote.exe","onenotem.exe","onenoteviewer.exe","onenoteim.exe", "msaccess.exe") ImageLoaded = "*\\taskschd.dll" | stats min(_time) as firstTime max(_time) as lastTime values(ImageLoaded) as AllImageLoaded count by Computer EventCode Image parent_process_name ProcessId ProcessGuid | rename Computer as dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `office_document_creating_schedule_task_filter`
The SPL above uses the following Macros:
office_document_creating_schedule_task_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 and ImageLoaded (Like sysmon EventCode 7) from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Also be sure to include those monitored dll to your own sysmon config.
Known False Positives
Associated Analytic Story
|49.0||70||70||Office document creating a schedule task on $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 4