Office (OOXML) malware analysis — malicious · 4172157c4e2af8af

MALICIOUS

Office (OOXML)

19.1 KB Created: 2021-07-29 14:19:00 UTC Authoring application: Microsoft Excel 16.0300

MD5: 6939eaf7808707f98765be7187c2ee73 SHA-1: dc32def04e11ee58bf171dd96421f8e294b3ff96 SHA-256: 4172157c4e2af8afae99ea967878b5ebccaf542b21389797a40f940dd357bfa4

322 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1218.011 Signed Binary Proxy Execution: Rundll32

This OOXML document contains a Workbook_Open macro that uses WScript.Shell and the Shell() function to execute obfuscated code. The script attempts to download and execute a second-stage payload, indicated by the use of CreateObject and the presence of a long, encoded blob within the VBA code. The obfuscation and execution methods suggest a downloader or dropper functionality.

Heuristics 8

Shell() call in VBA critical OLE_VBA_SHELL

Shell() call in VBA
WScript.Shell usage critical OLE_VBA_WSCRIPT

WScript.Shell usage
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
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `e49bddd7b3fe565897f34df508cf3ea8a5c2d4444e9b8d583b1b93ba50c30e78`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	7746 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 9 long base64-like blob(s).
`vbaProject_00.bin` `d54d2a3483ca0a1d761266beb21f3018399ce4c62a72e7f706b8e76efc35d085`	vba-project	OOXML VBA project: xl/vbaProject.bin	26624 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 9 long base64-like blob(s).

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