Office (OOXML) / .XLSX malware analysis — malicious · d8641ffe9ca7a1d0

MALICIOUS

Office (OOXML) / .XLSX

71.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 863b426ca29f861bd0757fedc4b58dfb SHA-1: effaf89487c6ff6df9db48a2a76993d7628c7f47 SHA-256: d8641ffe9ca7a1d045fa011eaec67cc60130fcde46d51825dbef16e5bc544340

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing a macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet itself is heavily obfuscated and truncated, making it impossible to determine the exact payload or its destination. However, the presence of Excel 4.0 macros strongly suggests an attempt to execute arbitrary code, commonly used for downloading and running secondary payloads.

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` `392cec0284ce120c4706881b72604f9a7149a2d0a0e8bfa5bd71064a42a66c11`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	6986 bytes

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