Office (OOXML) / .XLSX malware analysis — malicious · 866cba5d10b39dca

MALICIOUS

Office (OOXML) / .XLSX

106.5 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: 9223ca3fc057bfa36d4edca9ad50eaf7 SHA-1: 80b89aa9eb275a83de6e8ab95597b50fcd2a0573 SHA-256: 866cba5d10b39dca37d70d5e496569ecc30d4c76a626bed9e5a5bcd0fa8961ed

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. While the macro content is truncated and heavily obfuscated, this technique is commonly used to download and execute second-stage payloads. No specific IOCs could be extracted due to the truncation.

Heuristics 1

Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET

Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `9cb8004eb61eeee6ff6f603082d61a4c3ef794b2b7d053e69de5e13e61cd37d2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	288449 bytes

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