Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 f87dc297688155df…

MALICIOUS

Office (OOXML)

16.0 KB Created: 2021-05-18 11:57:42 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-05-22
MD5: 156bebd42b7c68f49aef91ba9ada2ecf SHA-1: e2f2455d77a9a04a2b6f300d7ff43219460e80a5 SHA-256: f87dc297688155df85844c18b7975a51817d1063498715b3d0dab5d5f0e057ab
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059 Command and Scripting Interpreter T1204.002 Malicious File

The OOXML document contains a VBA macro with an Auto_Open subroutine, which is a common technique for executing malicious code upon opening. The script decodes a Base64 string, "aGVsbG8gd29ybGQ=", which likely represents a command to download and execute a further payload. The use of CreateObject and the Auto_Open macro strongly suggest a macro-based downloader.

Heuristics 4

  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • 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.

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) 2334 bytes
SHA-256: 64994edafb98b457ed28c898e4cda49262c1e53216ce4211da266d5b51528094
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

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

Attribute VB_Name = "Module1"
Sub Auto_Open()


Dim cmd As String

cmd = "aGVsbG8gd29ybGQ="

End Sub


Function DecodeBase64(b64$)
    Dim b
    With CreateObject("Microsoft.XMLDOM").createElement("b64")
        .DataType = "bin.base64": .Text = b64
        b = .nodeTypedValue
        With CreateObject("ADODB.Stream")
            .Open: .Type = 1: .Write b: .Position = 0: .Type = 2: .Charset = "utf-8"
            DecodeBase64 = .ReadText
            .Close
        End With
    End With
End Function

Attribute VB_Name = "Sheet2"
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

Attribute VB_Name = "Sheet3"
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

Attribute VB_Name = "Sheet4"
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

Attribute VB_Name = "Sheet5"
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 19456 bytes
SHA-256: 8bd218a76cdc7911c0dc92fdbd3691eeb326c06f41df6511a0f6ec2c4fc88930

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