Office (OOXML) / .XLSX malware analysis — malicious · 2920bb77d97ba58e

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 94f762e9f5cf89bb61ce2958216f4017 SHA-1: 2de44f2dd8a45bdc6a6f0d77405f02853e6d9264 SHA-256: 2920bb77d97ba58ee96db57089f1977942295125f861eeb128c83775013c6d67

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The macro sheet contains obfuscated commands that appear to construct a path to a startup executable, 'C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Start-up\M.exe'. This suggests the macro's purpose is to download and execute a second-stage payload, likely for persistence or further infection.

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` `a7680250482d47b09af34c00b985fcffb9967906768e3635fd497d199ce98f55`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	8012 bytes

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