Office (OOXML) / .XLSX malware analysis — malicious · 84cdfdd7a4fd668e

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: d03243bd94ee00f862be9e3b19f5e4d5 SHA-1: b08de91b5f28708885224bcaabf1acafc8892ee6 SHA-256: 84cdfdd7a4fd668e61ebf604c8c84a2528d9837ba2571e5a13d244f4d3a4a5b7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an XLSX file containing a single Excel 4.0 macro sheet. The heuristic firing confirms the presence of these macros. The macro code appears to be obfuscated, but it attempts to create a shortcut file in the Windows Startup folder, likely to establish persistence for a downloaded payload. The specific reconstructed path is C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup\System.lnk. Due to the obfuscation, the exact download mechanism and payload are not fully discernible, leading to a moderate confidence score.

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` `130931cee197c2d9d9cb10dbc551d4a3a1d51415eb833af278c196422e568e0c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4456 bytes

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