Office (OOXML) / .XLSX malware analysis — malicious · 8ec7338b7b007944

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 3cacdcfbb9f99d0db91aaf24a639fcce SHA-1: 6237a0843c68e0dff88f56292bf7d405fbb588ac SHA-256: 8ec7338b7b007944aa8a20d4666d2a22afb8725a3bf288953afdd99a45d50e71

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. The extracted macro content, though heavily obfuscated and truncated, appears to reference a path that resembles a file name, 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to execute commands, potentially to download and run a secondary payload disguised as an RTF file. The confidence is moderate due to the obfuscated nature of the macro content.

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` `134200854417b5e862d28a136107ef37e7b59822203aaeb9020593734e511117`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	176401 bytes

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