Office (OOXML) / .XLSX malware analysis — malicious · c829f788d4a39f86

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: abd1f2b3a48f9a2273ae16b60ba90e8c SHA-1: 385868e77c4757649bcc5b7cd844730dcea893d9 SHA-256: c829f788d4a39f86dfcc9471906c4862d53788de6d3126590cbfdd5bc7e53e30

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros, a known technique for executing malicious code. The macro appears to be constructing paths within C:\ProgramData\Microsoft\Windows\ to drop and execute a payload, likely named 'a.exe'. The obfuscated nature of the macro prevents a more precise determination of its exact actions or a confident family attribution.

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` `06a6f93516613144ab5469bc49ad9e504d9ef81a065074b35a965bc3fb624ae6`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4672 bytes

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