269. That's How Adversaries Abuse Features of Winlogon

Hello everyone!

Today we'll look at another persistence mechanism, which you don't see ITW very often. I'm talking about the following technique - Boot or Logon Autostart Execution: Winlogon Helper DLL (T1547.004).

According to this report, the adversary modified Winlogon key in order to achieve persistence:

reg add '"hkcu\software\microsoft\windows nt\currentversion\winlogon'" /f /v Shell /t REG_SZ /d '"$($sv.Replace('"', '\"'))'""

 Such registry modification enables the malicious script to run at every user login along with explorer.exe.

At the same time, it's a detection opportunity for us:

event_type: "processcreatewin"

AND

proc_file_path: "reg.exe"

AND

cmdline: ("add" AND "winlogon" AND "shell")

See you tomorrow!


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