The following query utilizes Windows Security EventCode 4698,
A scheduled task was created, to identify suspicious tasks registered on Windows either via schtasks.exe OR TaskService with a command to be executed with a native Windows shell (PowerShell, Cmd, Wscript, Cscript).
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
The following DLL(s) are loaded when schtasks.exe or TaskService is launched -
taskschd.dll. If found loaded by another process, it is 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: 2021-04-12
- Author: Michael Haag, Splunk
- ID: 203ef0ea-9bd8-11eb-8201-acde48001122
Kill Chain Phase
1 2 3 4 5 6 7 `wineventlog_security` EventCode=4698 | xmlkv Message | search Command IN ("*powershell.exe*", "*wscript.exe*", "*cscript.exe*", "*cmd.exe*", "*sh.exe*", "*ksh.exe*", "*zsh.exe*", "*bash.exe*", "*scrcons.exe*", "*pwsh.exe*") | stats count min(_time) as firstTime max(_time) as lastTime by dest, Task_Name, Command, Author, Enabled, Hidden | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `winevent_scheduled_task_created_to_spawn_shell_filter`
The SPL above uses the following Macros:
winevent_scheduled_task_created_to_spawn_shell_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 Windows Security Event Logs with 4698 EventCode enabled. The Windows TA is also required.
Known False Positives
False positives are possible if legitimate applications are allowed to register tasks that call a shell to be spawned. Filter as needed based on command-line or processes that are used legitimately.
Associated Analytic Story
|70.0||70||100||A windows scheduled task was created (task name=$Task_Name$) on $dest$ by the following command: $Command$|
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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