Bypass User Account Control
Windows User Account Control (UAC) allows a program to elevate its privileges to perform a task under administrator-level permissions 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. 
If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs are allowed to elevate privileges or execute some elevated COM objects without prompting the user through the UAC notification box.   An example of this is use of rundll32.exe to load a specifically crafted DLL which loads an auto-elevated COM 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.  Adversaries can use these techniques to elevate privileges to administrator if the target process is unprotected.
Many methods have been discovered to bypass UAC. The Github readme page for UACMe contains an extensive list of methods  that have been discovered and implemented within UACMe, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:
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 lateral systems and default to high integrity. 
Remove users from the local administrator group on systems. 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.
Check for common UAC bypass weaknesses on Windows systems to be aware of the risk posture and address issues where appropriate. 
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:
eventvwr.exebypass uses the
[HKEY_CURRENT_USER]\Software\Classes\mscfile\shell\open\commandRegistry key. 
sdclt.exebypass uses the
[HKEY_CURRENT_USER]\Software\Classes\exefile\shell\runas\command\isolatedCommandRegistry keys.  
Analysts should monitor these Registry settings for unauthorized changes.
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