Detecting T1548 Abuse Elevation Control Mechanism

When to Use

• When hunting for privilege escalation via UAC bypass in Windows environments
• After threat intelligence indicates use of UAC bypass exploits by active threat groups
• When investigating how attackers achieved administrative access without triggering UAC prompts
• During security assessments to validate UAC bypass detection coverage
• When monitoring for setuid/setgid abuse on Linux systems

Prerequisites

• Sysmon Event ID 1 with command-line and parent process logging
• Windows Security Event ID 4688 with process tracking
• Registry auditing for UAC-related keys (HKCU\Software\Classes)
• Sysmon Event ID 12/13 (Registry key/value modification)
• EDR with elevation monitoring capabilities

Workflow

1. Monitor UAC Registry Modifications: Many UAC bypasses modify registry keys under HKCU\Software\Classes\ms-settings\shell\open\command or HKCU\Software\Classes\mscfile\shell\open\command. Track Sysmon Events 12/13 for these changes.
2. Detect Auto-Elevating Process Abuse: Certain Windows binaries auto-elevate without UAC prompts (fodhelper.exe, computerdefaults.exe, eventvwr.exe). Hunt for these being launched by non-standard parent processes.
3. Track Process Integrity Level Changes: Monitor for processes escalating from medium to high integrity level without corresponding UAC consent events.
4. Hunt for Elevated Process Spawning: Detect when auto-elevating processes spawn unexpected children (cmd.exe, powershell.exe) -- indicating UAC bypass exploitation.
5. Monitor Linux Elevation Abuse: Track sudo misconfiguration exploitation, setuid binary abuse, and capability manipulation.
6. Correlate with Privilege Escalation Chain: Map elevation abuse to the broader attack chain, identifying what was done with escalated privileges.

Key Concepts

Concept	Description
T1548.002	Bypass User Account Control
T1548.001	Setuid and Setgid (Linux)
T1548.003	Sudo and Sudo Caching
T1548.004	Elevated Execution with Prompt (macOS)
UAC Auto-Elevation	Windows binaries that elevate without prompt
fodhelper.exe	Common UAC bypass vector via registry hijack
eventvwr.exe	MSC file handler UAC bypass
Integrity Level	Windows process trust level (Low/Medium/High/System)

Detection Queries

Splunk -- UAC Bypass via Registry Modification

index=sysmon (EventCode=12 OR EventCode=13)
| where match(TargetObject, "(?i)HKCU\\\\Software\\\\Classes\\\\(ms-settings|mscfile|exefile|Folder)\\\\shell\\\\open\\\\command")
| table _time Computer User EventCode TargetObject Details Image

Splunk -- Auto-Elevating Process Abuse

index=sysmon EventCode=1
| where match(Image, "(?i)(fodhelper|computerdefaults|eventvwr|sdclt|slui|cmstp)\.exe$")
| where NOT match(ParentImage, "(?i)(explorer|svchost|services)\.exe$")
| table _time Computer User Image CommandLine ParentImage ParentCommandLine

KQL -- UAC Bypass Detection

DeviceRegistryEvents
| where Timestamp > ago(7d)
| where RegistryKey has_any ("ms-settings\\shell\\open\\command", "mscfile\\shell\\open\\command")
| where ActionType == "RegistryValueSet"
| project Timestamp, DeviceName, RegistryKey, RegistryValueData, InitiatingProcessFileName

Sigma Rule

title: UAC Bypass via Registry Modification
status: stable
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        TargetObject|contains:
            - '\ms-settings\shell\open\command'
            - '\mscfile\shell\open\command'
            - '\exefile\shell\open\command'
    condition: selection
level: high
tags:
    - attack.privilege_escalation
    - attack.t1548.002

Common Scenarios

1. fodhelper.exe Registry Hijack: Attacker sets HKCU\Software\Classes\ms-settings\shell\open\command to a malicious executable, then launches fodhelper.exe which auto-elevates and executes the hijacked command.
2. eventvwr.exe MSC Bypass: Modifying HKCU\Software\Classes\mscfile\shell\open\command to intercept Event Viewer's auto-elevation behavior.
3. sdclt.exe Bypass: Leveraging the Windows Backup utility's auto-elevation to execute arbitrary commands.
4. CMSTP.exe INF Bypass: Using Connection Manager Profile Installer with a malicious INF file to bypass UAC via /s /ni flags.
5. DLL Hijacking in Auto-Elevate: Placing malicious DLLs in search paths of auto-elevating executables.

Output Format

Hunt ID: TH-UAC-[DATE]-[SEQ]
Host: [Hostname]
Bypass Method: [Registry hijack/DLL hijack/Token manipulation]
Auto-Elevate Binary: [fodhelper.exe/eventvwr.exe/etc.]
Registry Key Modified: [Full registry path]
Payload Executed: [Command or binary path]
User Context: [Account]
Risk Level: [Critical/High/Medium]
ATT&CK Technique: [T1548.00x]