UAC Bypass Using NTFS Reparse Point - Process

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Christian Burkard (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the pattern of UAC Bypass using NTFS reparse point and wusa.exe DLL hijacking (UACMe 36)

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548.002` Abuse Elevation Control Mechanism: Bypass User Account Control

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: UAC Bypass Using NTFS Reparse Point - Process
id: 39ed3c80-e6a1-431b-9df3-911ac53d08a7
status: test
description: Detects the pattern of UAC Bypass using NTFS reparse point and wusa.exe DLL hijacking (UACMe 36)
references:
    - https://github.com/hfiref0x/UACME
author: Christian Burkard (Nextron Systems)
date: 2021-08-30
modified: 2024-12-01
tags:
    - attack.privilege-escalation
    - attack.t1548.002
logsource:
    category: process_creation
    product: windows
detection:
    selection1:
        CommandLine|startswith: '"C:\Windows\system32\wusa.exe"  /quiet C:\Users\'
        CommandLine|endswith: '\AppData\Local\Temp\update.msu'
        IntegrityLevel:
            - 'High'
            - 'System'
            - 'S-1-16-16384' # System
            - 'S-1-16-12288' # High
    selection2:
        ParentCommandLine: '"C:\Windows\system32\dism.exe" /online /quiet /norestart /add-package /packagepath:"C:\Windows\system32\pe386" /ignorecheck'
        IntegrityLevel:
            - 'High'
            - 'System'
        CommandLine|contains|all:
            - 'C:\Users\'
            - '\AppData\Local\Temp\'
            - '\dismhost.exe {'
        Image|endswith: '\DismHost.exe'
    condition: 1 of selection*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

1 of selection*

Stage 1: `selection1`

selection1:
    CommandLine|startswith: '"C:\Windows\system32\wusa.exe"  /quiet C:\Users\'
    CommandLine|endswith: '\AppData\Local\Temp\update.msu'
    IntegrityLevel:
        - 'High'
        - 'System'
        - 'S-1-16-16384'
        - 'S-1-16-12288'

Stage 2: `selection2`

selection2:
    ParentCommandLine: '"C:\Windows\system32\dism.exe" /online /quiet /norestart /add-package /packagepath:"C:\Windows\system32\pe386" /ignorecheck'
    IntegrityLevel:
        - 'High'
        - 'System'
    CommandLine|contains|all:
        - 'C:\Users\'
        - '\AppData\Local\Temp\'
        - '\dismhost.exe {'
    Image|endswith: '\DismHost.exe'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	ends_with	`\AppData\Local\Temp\update.msu`	`field:"CommandLine" kind:ends_with value:"\AppData\Local\Temp\update.msu"`
`CommandLine`	match	`C:\Users\` corpus 7 (sigma 7) `\AppData\Local\Temp\` corpus 28 (sigma 26, elastic 2) `\dismhost.exe {`	`field:"CommandLine" kind:match`
`CommandLine`	starts_with	`"C:\Windows\system32\wusa.exe" /quiet C:\Users\`	`field:"CommandLine" kind:starts_with`
`Image`	ends_with	`\DismHost.exe` corpus 2 (sigma 2)	`field:"Image" kind:ends_with value:"\DismHost.exe"`
`IntegrityLevel`	eq	`High` corpus 21 (sigma 17, kusto 3, splunk 1) `S-1-16-12288` corpus 21 (sigma 17, kusto 3, splunk 1) `S-1-16-16384` corpus 30 (sigma 22, splunk 4, elastic 3, kusto 1) `System` corpus 30 (sigma 22, splunk 4, elastic 3, kusto 1)	`field:"IntegrityLevel" kind:eq`
`ParentCommandLine`	eq	`"C:\Windows\system32\dism.exe" /online /quiet /norestart /add-package /packagepath:"C:\Windows\system32\pe386" /ignorecheck`	`field:"ParentCommandLine" kind:eq`

UAC Bypass Using NTFS Reparse Point - Process

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection1

Stage 2: selection2

Indicators

Stage 0: `condition`

Stage 1: `selection1`

Stage 2: `selection2`