Office (OOXML) / .XLSX malware analysis — malicious · 6440c517ffee4597

MALICIOUS

Office (OOXML) / .XLSX

45.4 KB Created: 2021-07-08 06:35:50 UTC Authoring application: Microsoft Excel 15.0300

MD5: f75921fb937644a4f11f912508c1c96d SHA-1: 8e55ac18331fe1caa099fe372dc8f2a9b4190050 SHA-256: 6440c517ffee4597f50836eb8d40258ccca1055cffc6498a2e071ec0e23fcc94

202 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059 Command and Scripting Interpreter T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The file contains a Workbook_Open VBA macro that executes obfuscated code. This code uses CreateObject and appears to be a loader designed to download and execute a second-stage payload. The obfuscation and auto-execution mechanism suggest a malicious intent, likely delivered via spearphishing.

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
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` `9cde51bcfa4bcf85f4f4f67809bb26296652e82309064ca27676c3b299e336ab`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	5470 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 6 long base64-like blob(s).
`vbaProject_00.bin` `2b1e6c7071eaf9cb3c0e8ddb27f54ea206d058fe13bea4b043146c5d456baebc`	vba-project	OOXML VBA project: xl/vbaProject.bin	21504 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 6 long base64-like blob(s).

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