Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 9cd8dd7d42350dc0…

MALICIOUS

Office (OOXML)

231.4 KB Created: 2021-06-20 15:50:25 UTC Authoring application: Microsoft Excel 16.0300
MD5: 6a05ad7ecab105411f6d23d8a1bcb95a SHA-1: bd3ebc16b2a30619582f9bc261a67bb228547f16 SHA-256: 9cd8dd7d42350dc0aeecbc66bcd3283d789bcd9eba89f8a3368e002a5376f3a0
208 Risk Score

Malware Insights

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

The critical heuristic 'Obfuscated auto-exec VBA loader' and the high-severity 'Workbook_Open macro' firing indicate that the document is designed to automatically execute VBA code upon opening. The Workbook_Open subroutine calls Application.Run, which is used to execute obfuscated VBA functions. This pattern strongly suggests the macro is a loader for a second-stage payload, likely downloaded from an external source, aligning with the Spearphishing Attachment initial access technique.

Heuristics 6

  • Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER
    Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_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.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
2d30690d1c78e8e74f1e83133ae6421f3f78cdeb60195acaf42e62d5a8ecc4da		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 108153 bytes
vbaProject_00.bin
c9337f66e791a32912a7105709b500cd6d58502956629cf8ab61b527102f9995		 vba-project OOXML VBA project: xl/vbaProject.bin 842752 bytes
emf_00.emf
181321227cb9df20544fd6474137d964a19836fb544706c1dd27a5c0622aec7b		 ooxml-emf OOXML EMF part: xl/media/image1.emf 2672 bytes

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