Office (OOXML) / .XLSX malware analysis — malicious · 8fb49ddb6f0a8015

MALICIOUS

Office (OOXML) / .XLSX

73.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2021-11-07

MD5: b6b4e24168a62acf632b84a68f78dc19 SHA-1: b26f2f229efed60df229e80fba58616f7b3bf272 SHA-256: 8fb49ddb6f0a80159141d618c7ad7306cd733790043ac91611cac399e8a51dd7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The embedded macro sheet contains strings that appear to construct a path to 'C:\ProgramData\Microsoft\Excel.rtf'. This suggests the macro's intent is to write or manipulate a file at this location, likely as part of a payload delivery or execution chain. The macro's functionality is not fully discernible due to truncation, but its presence and the constructed path point to a malicious downloader or dropper.

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` `5451436734432d68c05c273f044cea85ab265b05ceffd306d8e5d2e90b4e80a1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	108718 bytes

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