Office (OOXML) / .XLSX malware analysis — malicious · 8c39b5dd896e4b71

MALICIOUS

Office (OOXML) / .XLSX

240.7 KB Created: 2021-03-31 07:49:17 UTC Authoring application: Microsoft Excel 16.0300

MD5: cc029b8675d3b262564d4d81c6008d5b SHA-1: 8ff96b31ed0dc8689d868dcabc610aa3efbbe13c SHA-256: 8c39b5dd896e4b7163f0c9f27b3ecde4435fa98666cd6e8e1f0a7df73ed757f7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet, which is a common delivery mechanism for malicious macros. While the script content is truncated and obfuscated, the presence of such a sheet strongly suggests an intent to execute arbitrary code, typically for downloading and executing a second-stage payload. The macro sheet itself is the primary indicator of malicious activity in this sample.

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` `f191af2491005ffcb6398ef50e417921af3842b18daff144cf5141265799c74a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	2288 bytes

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