Office (OOXML) / .XLSX malware analysis — malicious · 9dc3953c173bdb1f

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 4121e7f152ee4deefc4709a294801661 SHA-1: 7ceddd63cfbfd09d0d6f2bdd7ab469eaff3cff29 SHA-256: 9dc3953c173bdb1ffacd6ad0e94ee5757bbc6b0268fd2b8d331996e2d379b450

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic 'OOXML_XLM_MACROSHEET' indicates the presence of Excel 4.0 macros within the XLSX file. The extracted macro content, though partially truncated, shows a clear attempt to write a file named 'excel.rtf' to the 'C:\ProgramData\' directory. This suggests the macro is designed to download and execute a second-stage payload, a common technique for initial access.

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` `265aa4d34675dc2c6c210293ceff3902f61d78166b4d197746d295193a940af8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	95929 bytes

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