Abuse Elevation Control Mechanism: Bypass User Account Control

Adversaries may bypass UAC mechanisms to elevate process privileges on system. Windows User Account Control (UAC) allows a program to elevate its privileges (tracked as integrity levels ranging from low to high) to perform a task under administrator-level permissions, possibly by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action. [1]

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs can elevate privileges or execute some elevated Component Object Model objects without prompting the user through the UAC notification box. [2] [3] An example of this is use of Rundll32 to load a specifically crafted DLL which loads an auto-elevated Component Object Model object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user.[4]

Many methods have been discovered to bypass UAC. The Github readme page for UACME contains an extensive list of methods[5] that have been discovered and implemented, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

  • eventvwr.exe can auto-elevate and execute a specified binary or script.[6][7]

Another bypass is possible through some lateral movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on remote systems and default to high integrity.[8]

ID: T1548.002
Sub-technique of:  T1548
Tactics: Privilege Escalation, Defense Evasion
Platforms: Windows
Permissions Required: Administrator, User
Effective Permissions: Administrator
Data Sources: Command: Command Execution, Process: Process Creation, Process: Process Metadata, Windows Registry: Windows Registry Key Modification
Defense Bypassed: Windows User Account Control
Contributors: Casey Smith; Stefan Kanthak
Version: 2.0
Created: 30 January 2020
Last Modified: 22 July 2020

Procedure Examples

ID Name Description
S0584 AppleJeus

AppleJeus has presented the user with a UAC prompt to elevate privileges while installing.[9]

G0016 APT29

APT29 has bypassed UAC.[10]

G0067 APT37

APT37 has a function in the initial dropper to bypass Windows UAC in order to execute the next payload with higher privileges.[11]

S0129 AutoIt backdoor

AutoIt backdoor attempts to escalate privileges by bypassing User Access Control.[12]

S0570 BitPaymer

BitPaymer can suppress UAC prompts by setting the HKCU\Software\Classes\ms-settings\shell\open\command registry key on Windows 10 or HKCU\Software\Classes\mscfile\shell\open\command on Windows 7 and launching the eventvwr.msc process, which launches BitPaymer with elevated privileges.[13]

S0089 BlackEnergy

BlackEnergy attempts to bypass default User Access Control (UAC) settings by exploiting a backward-compatibility setting found in Windows 7 and later.[14]

G0060 BRONZE BUTLER

BRONZE BUTLER has used a Windows 10 specific tool and xxmm to bypass UAC for privilege escalation.[15][16]

G0080 Cobalt Group

Cobalt Group has bypassed UAC.[17]

S0154 Cobalt Strike

Cobalt Strike can use a number of known techniques to bypass Windows UAC.[18]

S0527 CSPY Downloader

CSPY Downloader can bypass UAC using the SilentCleanup task to execute the binary with elevated privileges.[19]

S0134 Downdelph

Downdelph bypasses UAC to escalate privileges by using a custom "RedirectEXE" shim database.[20]

S0363 Empire

Empire includes various modules to attempt to bypass UAC for escalation of privileges.[21]

G0120 Evilnum

Evilnum has used PowerShell to bypass UAC.[22]

S0182 FinFisher

FinFisher performs UAC bypass.[23][24]

S0531 Grandoreiro

Grandoreiro can bypass UAC by registering as the default handler for .MSC files.[25]

S0132 H1N1

H1N1 bypasses user access control by using a DLL hijacking vulnerability in the Windows Update Standalone Installer (wusa.exe).[26]

G0072 Honeybee

Honeybee uses a combination of NTWDBLIB.dll and cliconfg.exe to bypass UAC protections using DLL hijacking.[27]

S0260 InvisiMole

InvisiMole can use fileless UAC bypass and create an elevated COM object to escalate privileges.[28][29]

S0250 Koadic

Koadic has 2 methods for elevating integrity. It can bypass UAC through eventvwr.exe and sdclt.exe.[30]

S0356 KONNI

KONNI bypassed UAC with the "AlwaysNotify" settings.[31]

G0069 MuddyWater

MuddyWater uses various techniques to bypass UAC.[32]

G0040 Patchwork

Patchwork bypassed User Access Control (UAC).[33]

S0501 PipeMon

PipeMon installer can use UAC bypass techniques to install the payload.[34]

S0254 PLAINTEE

An older variant of PLAINTEE performs UAC bypass.[35]

S0378 PoshC2

PoshC2 can utilize multiple methods to bypass UAC.[36]

S0192 Pupy

Pupy can bypass Windows UAC through either DLL hijacking, eventvwr, or appPaths.[37]

S0458 Ramsay

Ramsay can use UACMe for privilege escalation.[38][39]

S0332 Remcos

Remcos has a command for UAC bypassing.[40]

S0148 RTM

RTM can attempt to run the program as admin, then show a fake error message and a legitimate UAC bypass prompt to the user in an attempt to socially engineer the user into escalating privileges.[41]

S0074 Sakula

Sakula contains UAC bypass code for both 32- and 64-bit systems.[42]

S0140 Shamoon

Shamoon attempts to disable UAC remote restrictions by modifying the Registry.[43]

S0444 ShimRat

ShimRat has hijacked the cryptbase.dll within migwiz.exe to escalate privileges. This prevented the User Access Control window from appearing.[44]

G0027 Threat Group-3390

A Threat Group-3390 tool can use a public UAC bypass method to elevate privileges.[45]

S0116 UACMe

UACMe contains many methods for bypassing Windows User Account Control on multiple versions of the operating system.[5]

S0230 ZeroT

Many ZeroT samples can perform UAC bypass by using eventvwr.exe to execute a malicious file.[46]

Mitigations

ID Mitigation Description
M1047 Audit

Check for common UAC bypass weaknesses on Windows systems to be aware of the risk posture and address issues where appropriate.[5]

M1026 Privileged Account Management

Remove users from the local administrator group on systems.

M1051 Update Software

Consider updating Windows to the latest version and patch level to utilize the latest protective measures against UAC bypass.[5]

M1052 User Account Control

Although UAC bypass techniques exist, it is still prudent to use the highest enforcement level for UAC when possible and mitigate bypass opportunities that exist with techniques such as DLL Search Order Hijacking.

Detection

There are many ways to perform UAC bypasses when a user is in the local administrator group on a system, so it may be difficult to target detection on all variations. Efforts should likely be placed on mitigation and collecting enough information on process launches and actions that could be performed before and after a UAC bypass is performed. Monitor process API calls for behavior that may be indicative of Process Injection and unusual loaded DLLs through DLL Search Order Hijacking, which indicate attempts to gain access to higher privileged processes.

Some UAC bypass methods rely on modifying specific, user-accessible Registry settings. For example:

  • The eventvwr.exe bypass uses the [HKEY_CURRENT_USER]\Software\Classes\mscfile\shell\open\command Registry key.[6]

  • The sdclt.exe bypass uses the [HKEY_CURRENT_USER]\Software\Microsoft\Windows\CurrentVersion\App Paths\control.exe and [HKEY_CURRENT_USER]\Software\Classes\exefile\shell\runas\command\isolatedCommand Registry keys.[47][48]

Analysts should monitor these Registry settings for unauthorized changes.

References

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  2. Russinovich, M. (2009, July). User Account Control: Inside Windows 7 User Account Control. Retrieved July 26, 2016.
  3. Microsoft. (n.d.). The COM Elevation Moniker. Retrieved July 26, 2016.
  4. Davidson, L. (n.d.). Windows 7 UAC whitelist. Retrieved November 12, 2014.
  5. UACME Project. (2016, June 16). UACMe. Retrieved July 26, 2016.
  6. Nelson, M. (2016, August 15). "Fileless" UAC Bypass using eventvwr.exe and Registry Hijacking. Retrieved December 27, 2016.
  7. Salvio, J., Joven, R. (2016, December 16). Malicious Macro Bypasses UAC to Elevate Privilege for Fareit Malware. Retrieved December 27, 2016.
  8. Medin, T. (2013, August 8). PsExec UAC Bypass. Retrieved June 3, 2016.
  9. Cybersecurity and Infrastructure Security Agency. (2021, February 21). AppleJeus: Analysis of North Korea’s Cryptocurrency Malware. Retrieved March 1, 2021.
  10. Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016.
  11. GReAT. (2019, May 13). ScarCruft continues to evolve, introduces Bluetooth harvester. Retrieved June 4, 2019.
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  13. Frankoff, S., Hartley, B. (2018, November 14). Big Game Hunting: The Evolution of INDRIK SPIDER From Dridex Wire Fraud to BitPaymer Targeted Ransomware. Retrieved January 6, 2021.
  14. F-Secure Labs. (2014). BlackEnergy & Quedagh: The convergence of crimeware and APT attacks. Retrieved March 24, 2016.
  15. Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
  16. Chen, J. et al. (2019, November). Operation ENDTRADE: TICK’s Multi-Stage Backdoors for Attacking Industries and Stealing Classified Data. Retrieved June 9, 2020.
  17. Matveeva, V. (2017, August 15). Secrets of Cobalt. Retrieved October 10, 2018.
  18. Strategic Cyber LLC. (2017, March 14). Cobalt Strike Manual. Retrieved May 24, 2017.
  19. Dahan, A. et al. (2020, November 2). Back to the Future: Inside the Kimsuky KGH Spyware Suite. Retrieved November 6, 2020.
  20. ESET. (2016, October). En Route with Sednit - Part 3: A Mysterious Downloader. Retrieved November 21, 2016.
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  1. ESET. (2020, April 28). Grandoreiro: How engorged can an EXE get?. Retrieved November 13, 2020.
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  3. Sherstobitoff, R. (2018, March 02). McAfee Uncovers Operation Honeybee, a Malicious Document Campaign Targeting Humanitarian Aid Groups. Retrieved May 16, 2018.
  4. Hromcová, Z. (2018, June 07). InvisiMole: Surprisingly equipped spyware, undercover since 2013. Retrieved July 10, 2018.
  5. Hromcova, Z. and Cherpanov, A. (2020, June). INVISIMOLE: THE HIDDEN PART OF THE STORY. Retrieved July 16, 2020.
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  7. Karmi, D. (2020, January 4). A Look Into Konni 2019 Campaign. Retrieved April 28, 2020.
  8. ClearSky Cyber Security. (2018, November). MuddyWater Operations in Lebanon and Oman: Using an Israeli compromised domain for a two-stage campaign. Retrieved November 29, 2018.
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  12. Nettitude. (2018, July 23). Python Server for PoshC2. Retrieved April 23, 2019.
  13. Nicolas Verdier. (n.d.). Retrieved January 29, 2018.
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