LoFP LoFP / false positives may occur if legitimate office documents are creating scheduled tasks. ensure to investigate the scheduled task and the command to be executed. if the task is benign, add the task name to the exclusion list. some applications may legitimately load taskschd.dll.

Techniques

Sample rules

Office Document Creating Schedule Task

Description

The following analytic detects a potentially malicious office document that creates a scheduled task entry either through a macro VBA API or by loading taskschd.dll. This technique has been observed in numerous instances of malicious macro malware aiming to establish persistence or beaconing through task schedule entries. The analytic will return the first and last time the task was registered, as well as details such as the Command to be executed, Task Name, Author, Enabled status, and whether it is Hidden. schtasks.exe is natively located in C:\Windows\system32 and C:\Windows\syswow64. The DLL(s) taskschd.dll are loaded when schtasks.exe or TaskService is initiated. If this DLL is found loaded by another process, it may indicate that a scheduled task is being registered within that process’s context in memory. During triage, determine the source of the scheduled task. Was it schtasks.exe or via TaskService? Review the job created and the command to be executed. Capture any artifacts on disk for further review. Identify any parallel processes within the same timeframe to pinpoint the source.'

Detection logic

`sysmon` EventCode=7 process_name IN ("WINWORD.EXE", "EXCEL.EXE", "POWERPNT.EXE","onenote.exe","onenotem.exe","onenoteviewer.exe","onenoteim.exe", "msaccess.exe") loaded_file_path = "*\\taskschd.dll" 
| stats min(_time) as firstTime max(_time) as lastTime count by user_id, dest, process_name,loaded_file, loaded_file_path, original_file_name, process_guid 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `office_document_creating_schedule_task_filter`