189. Adversaries Abuse ComputerDefaults.exe to Bypass the UAC

Hello everyone!

There're quite a few well-known ways to bypass the User Account Control (UAC). Some are often used in-the-wild, some are not.

Let's look at a recent example from Kaspersky report on Batavia spyware. The adversary abused ComputerDefaults.exe to bypass UAC. To do it, the threat actor modified two registry keys using reg.exe:

reg add HKCU\Software\Classes\ms-settings\Shell\Open\command /v DelegateExecute /t REG_SZ /d "" /f

reg add HKCU\Software\Classes\ms-settings\Shell\Open\command /f /ve /t REG_SZ /d "%temp%\windowsmsg.exe <arg>"

It means we can hunt for related registry keys modification events:

event_type: "registryvaluesetwin"

AND

reg_key_path: "ms-settings\\shell\\open\\command"

Also, check for suspicious processes spawned as a child process of ComputerDefaults.exe:

event_type: "processcreatewin"

AND

proc_p_file_path: "computerdefaults.exe"

See you tomorrow!

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