Office (OOXML) / .XLSX malware analysis — malicious · 22768a52769efaa1

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: a7b8838cfdb9a143542d409d92a18015 SHA-1: 6291152fc4d58908fbe6b985a61fb2e57c76ac8e SHA-256: 22768a52769efaa1e0779164dcc6d0b41bb74fa27b7e48db4d815b41d6b33df5

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 embedded macro sheet contains obfuscated strings that reconstruct to a file path, 'C:\ProgramData\excel.rtf', suggesting the macro's purpose is to download and execute a second-stage payload from this location. Due to the obfuscation and truncation of the macro content, the exact download mechanism and final 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` `e4f944a6e7d0dc0eaad013f809e8245d7ada3287b4669da4681de270c6197a80`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	106687 bytes

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