Randomly Generated Scheduled Task Name
THIS IS A EXPERIMENTAL DETECTION
This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.
The following hunting analytic leverages Event ID 4698,
A scheduled task was created, to identify the creation of a Scheduled Task with a suspicious, high entropy, Task Name. To achieve this, this analytic also leverages the
ut_shannon function from the URL ToolBox Splunk application. Red teams and adversaries alike may abuse the Task Scheduler to create and start a remote Scheduled Task and obtain remote code execution. To achieve this goal, tools like Impacket or Crapmapexec, typically create a Scheduled Task with a random task name on the victim host. This hunting analytic may help defenders identify Scheduled Tasks created as part of a lateral movement attack. The entropy threshold
ut_shannon > 3 should be customized by users. The Command field can be used to determine if the task has malicious intent or not.
- Type: Hunting
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-11-29
- Author: Mauricio Velazco, Splunk
- ID: 9d22a780-5165-11ec-ad4f-3e22fbd008af
Kill Chain Phase
1 2 3 4 5 6 `wineventlog_security` EventCode=4698 | xmlkv Message | lookup ut_shannon_lookup word as Task_Name | where ut_shannon > 3 | table _time, dest, Task_Name, ut_shannon, Command, Author, Enabled, Hidden | `randomly_generated_scheduled_task_name_filter`
The SPL above uses the following Macros:
randomly_generated_scheduled_task_name_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 as well as the URL ToolBox application are also required.
Known False Positives
Legitimate applications may use random Scheduled Task names.
Associated Analytic Story
|45.0||90||50||A windows scheduled task with a suspicious task name was created 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.
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replay.py tool or the UI.
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source | version: 1