397. Using Adversaries' Stealth Against Them

Hello everyone!

Today we'll talk about stealth and persistence in a compromised system, focusing on the following technique: Hidden Window (T1564.003).

I'm sure that searching for suspicious values in the Run registry key is part of your Threat Hunting routine. But sometimes attackers, while trying to stay hidden, actually help us detect malicious activity.

For example, EtherRAT wrote to HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\SecurityHealth the following value:

"C:\Windows\System32\conhost.exe" --headless "C:\Users\Bruno\AppData\Local\Adobe\Components\e8b3\node-v18.17.0-win-x64\node.exe" "C:\Users\Bruno\AppData\Local\Adobe\Components\e8b3\97f04949151a3819.js"

As you can see, the attackers used conhost.exe with the --headless parameter to hide the window. But how often would such a command chain be legitimately written to the Run key? Of course, almost never.

That gives us another detection opportunity:

event_type: "registryvaluesetwin"

AND

reg_key_path: "currentversion\run"

AND

reg_value_data: *conhost*

See you soon!

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