Office (OOXML) / .XLSX malware analysis — malicious · 9ce1fb8836f52602

MALICIOUS

Office (OOXML) / .XLSX

63.2 KB Created: 2021-03-14 21:03:54 UTC Authoring application: Microsoft Excel 16.0300

MD5: 1d0ebdfc4b1b359c23579844c8eaeb01 SHA-1: b6a6808de5a3ed613116debc238c040d96337829 SHA-256: 9ce1fb8836f5260297979597bd409e16d3fd6a651414a827fa7eb7f2961f74a3

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The embedded macro sheet contains obfuscated commands that are typical of macro-based malware. While the exact commands are truncated and heavily obfuscated, the presence of an XLM macro sheet strongly suggests an attempt to download and execute a secondary payload. The lack of clear URLs or specific commands prevents a higher confidence score or more detailed IOCs.

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` `0032456c6b60bc5da56d1dd3d74775adeef966de290e38cd4aa3468493ef505c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	92099 bytes

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