Windows Registry: Delete SD Value Under Schedule\TaskCache\Tree to Impair Scheduled Task Visibility

Detects deletion of the SD registry value under Schedule\TaskCache\Tree, which can impair scheduled task visibility.

FreeReviewedSigma · Medium · v1

Product: windows
Category: registry_delete
Author: Sittikorn S (SigmaHQ), DRL 1.1
Published: 2022-04-15
Updated: 2026-07-30

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags registry deletions that remove the SD value under the Schedule\TaskCache\Tree path in Windows. Attackers can use this defense-impairment behavior to hide or disrupt scheduled task visibility by altering security descriptor-related data. It relies on telemetry indicating registry value deletion events with a target object path containing the specified Schedule\TaskCache\Tree key and including an SD value.

Reporting behind it

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Windows Registry: Delete SD Value Under Schedule\TaskCache\Tree to Impair Scheduled Task Visibility

Pivot detection · T1685 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-registry-delete-sd-value-under-schedule-taskcache-tree-to-impair-schedul-acd74772

title: "Windows Registry: Delete SD Value Under Schedule\\TaskCache\\Tree to Impair Scheduled Task Visibility"
id: 211317d2-7618-495b-9749-996954c692ab
related:
  - id: 526cc8bc-1cdc-48ad-8b26-f19bff969cec
    type: similar
  - id: acd74772-5f88-45c7-956b-6a7b36c294d2
    type: derived
status: test
description: This rule flags registry deletions that remove the SD value under the Schedule\TaskCache\Tree path in Windows. Attackers can use this defense-impairment behavior to hide or disrupt scheduled task visibility by altering security descriptor-related data. It relies on telemetry indicating registry value deletion events with a target object path containing the specified Schedule\TaskCache\Tree key and including an SD value.
references:
  - https://www.microsoft.com/security/blog/2022/04/12/tarrask-malware-uses-scheduled-tasks-for-defense-evasion/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_delete/registry_delete_schtasks_hide_task_via_sd_value_removal.yml
author: Sittikorn S, Huntrule Team
date: 2022-04-15
modified: 2025-10-25
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  product: windows
  category: registry_delete
detection:
  selection:
    TargetObject|contains|all:
      - \SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree\
      - SD
  condition: selection
falsepositives:
  - Unknown
level: medium
regression_tests_path: regression_data/rules/windows/registry/registry_delete/registry_delete_schtasks_hide_task_via_sd_value_removal/info.yml
license: DRL-1.1

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