Scheduled Task Hide

id: 6dd2629c-534b-4275-8201-d7968b4fa77e
name: Scheduled Task Hide
description: |
   'This query detects attempts by malware to hide the scheduled task by deleting the SD (Security Descriptor) value. Removal of SD value results in the scheduled task disappearing from schtasks /query and Task Scheduler.
    The query requires auditing to be turned on for HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree registry hive as well as audit policy for registry auditing to be turned on.
    Reference: https://www.microsoft.com/security/blog/2022/04/12/tarrask-malware-uses-scheduled-tasks-for-defense-evasion/
    Reference: https://4sysops.com/archives/audit-changes-in-the-windows-registry/'
severity: High
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes:
      - SecurityEvent
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1562
tags:
  - Tarrask
query: |
  SecurityEvent
  | where EventID == 4657
  | extend EventData = parse_xml(EventData).EventData.Data
  | mv-expand bagexpansion=array EventData
  | evaluate bag_unpack(EventData)
  | extend Key = tostring(column_ifexists('@Name', "")), Value = column_ifexists('#text', "")
  | evaluate pivot(Key, any(Value), TimeGenerated, TargetAccount, Computer, EventSourceName, Channel, Task, Level, EventID, Activity, TargetLogonId, SourceComputerId, EventOriginId, Type, _ResourceId, TenantId, SourceSystem, ManagementGroupName, IpAddress, Account)
  | extend ObjectName = column_ifexists('ObjectName', ""), OperationType = column_ifexists('OperationType', ""), ObjectValueName = column_ifexists('ObjectValueName', "")
  | where ObjectName has 'Schedule\\TaskCache\\Tree' and ObjectValueName == "SD" and OperationType == "%%1906"  // %%1906 - Registry value deleted
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | extend AccountName = tostring(split(TargetAccount, @'\')[1]), AccountNTDomain = tostring(split(TargetAccount, @'\')[0])
  | extend timestamp = TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: TargetAccount
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: AccountNTDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
version: 1.0.1
kind: Scheduled