Office (OOXML) / .XLSX malware analysis — malicious · b65d90916a662392

MALICIOUS

Office (OOXML) / .XLSX

64.7 KB Created: 2021-03-15 18:27:04 UTC Authoring application: Microsoft Excel 16.0300

MD5: 4e43ebe63bf2c30c687b510d108b08fd SHA-1: de2084101cc574647af4d2e2370000797895c17d SHA-256: b65d90916a662392dad1f77cd64a84f5604fd1a72f1944bed0b40f3838492c35

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Execution

The sample is an Excel file containing an Excel 4.0 macro sheet, as indicated by the OOXML_XLM_MACROSHEET heuristic. While the macro content is truncated and heavily obfuscated, the presence of this macro sheet strongly suggests an attempt to execute arbitrary code. This is a common technique for delivering secondary payloads, such as downloaders or droppers, which aligns with a malicious intent.

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` `d9416cee0f43a10323ae7970a01f611ec955c8fdc1e4f4b33e25ab612961731c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	92701 bytes

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