Bypass UAC Using SilentCleanup Task

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About the rule

Rule Type

Standard

Rule 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.

Severity

Trouble

Rule Requirement

Criteria

Action1: actionname = "Registry value modified" AND (OBJECTNAME endswith "\Environment\windir" OR (OBJECTNAME endswith "\Environment" AND OBJECTVALUENAME = "windir")) AND INFORMATION != "%SystemRoot%" select Action1.HOSTNAME,Action1.MESSAGE,Action1.OBJECTNAME,Action1.PROCESSNAME,Action1.PREVVAL,Action1.CHANGES

Detection

Execution Mode

realtime

Log Sources

Windows

Author

frack113, Nextron Systems