Office (OOXML) / .XLSX malware analysis — malicious · a77d66e37425c821

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: fd4f08f685a1190db305d27f4b9fe700 SHA-1: 3095e88622663e3f1a54232f5ca6faa4fc2d1515 SHA-256: a77d66e37425c8210de308a8617f5214d0a96393577ac1bd30473e73a82dd73e

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, which is a strong indicator of malicious intent. The embedded Excel 4.0 macro sheet, when executed, likely attempts to write and execute a file named 'excel.rtf' to the 'C:\ProgramData\' directory. This suggests a downloader or initial execution stage for further malicious activity.

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` `d7e1f5e6597e2042851cfeffc5f40a037fd7cf5d0353441c05cb1a58ebc6833a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	92943 bytes

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