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Detection rules › Sigma

Bypass UAC Using SilentCleanup Task

Status
test
Severity
high
Log source
product windows, category registry_set
Author
frack113, Nextron Systems
Source
github.com/SigmaHQ/sigma

Detects the setting of the environement variable "windir" to a non default value. Attackers often abuse this variable in order to trigger a UAC bypass via the "SilentCleanup" task. The SilentCleanup task located in %windir%\system32\cleanmgr.exe is an auto-elevated task that can be abused to elevate any file with administrator privileges without prompting UAC.

MITRE ATT&CK coverage

TacticTechniques
Privilege EscalationT1548.002 Abuse Elevation Control Mechanism: Bypass User Account Control

Event coverage

ProviderEventTitle
SysmonEvent ID 13RegistryEvent (Value Set)

Rule body yaml

title: Bypass UAC Using SilentCleanup Task
id: 724ea201-6514-4f38-9739-e5973c34f49a
status: test
description: |
    Detects the setting of the environement variable "windir" to a non default value.
    Attackers often abuse this variable in order to trigger a UAC bypass via the "SilentCleanup" task.
    The SilentCleanup task located in %windir%\system32\cleanmgr.exe is an auto-elevated task that can be abused to elevate any file with administrator privileges without prompting UAC.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1548.002/T1548.002.md#atomic-test-9---bypass-uac-using-silentcleanup-task
    - https://www.reddit.com/r/hacking/comments/ajtrws/bypassing_highest_uac_level_windows_810/
    - https://www.fortinet.com/blog/threat-research/enter-the-darkgate-new-cryptocurrency-mining-and-ransomware-campaign
author: frack113, Nextron Systems
date: 2022-01-06
modified: 2024-01-30
tags:
    - attack.privilege-escalation
    - attack.t1548.002
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Environment\windir'
    filter_main_default:
        Details: '%SystemRoot%'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/registry/registry_set/registry_set_bypass_uac_using_silentcleanup_task/info.yml
simulation:
    - type: atomic-red-team
      name: Bypass UAC using SilentCleanup Task
      technique: T1548.002
      atomic_guid: 28104f8a-4ff1-4582-bcf6-699dce156608

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    TargetObject|endswith: '\Environment\windir'

Stage 2: not filter_main_default

filter_main_default:
    Details: '%SystemRoot%'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
Detailseq%SystemRoot%

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
TargetObjectends_with
  • \Environment\windir corpus 2 (sigma 1, elastic 1)