Office (OOXML) / .XLSM malware analysis — malicious · 678ce62c5d45c856

MALICIOUS

Office (OOXML) / .XLSM

434.9 KB Created: 2021-07-28 10:37:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: 5b1e9f4b5399aebfdf5ccd50115cb906 SHA-1: c9b6890294903e6520787031d010e500b9196581 SHA-256: 678ce62c5d45c856692960c05ee0f614d33b678c2f87f03d9988054c4af8067c

208 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The critical heuristic 'Obfuscated auto-exec VBA loader' and the presence of a Workbook_Open macro indicate malicious intent. The VBA script constructs a path to a script file using Environ() and then executes it via mshta.exe. The script also attempts to establish persistence by writing to the Run key.

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 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `24bfe7da4d2f0b7cf341c3bb09ca5a8c7702e2ead050ac5da047f34f5692ef87`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	1143 bytes
`vbaProject_00.bin` `ab76e16261637f98ee069c5be29e53a5fae05729181a0e7b658db07c1a34a072`	vba-project	OOXML VBA project: xl/vbaProject.bin	9216 bytes

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