Office (OOXML) / .XLSX malware analysis — malicious · df341e431a6cffdd

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e9cbcbdddf76bacba6e8d6b7c63b701d SHA-1: 6db73a05ea56a6d76e2e80484a48c659bd625be0 SHA-256: df341e431a6cffdd58ef2cc3ab095434681fc43d3203ecd6cbfe2350cfee10b6

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. Analysis of the macro content reveals it attempts to write a file named 'excel.rtf' to 'C:\ProgramData\'. This suggests the macro is designed to download and execute a second-stage payload, a common technique for initial access and further system compromise. The macro's obfuscated nature and truncated content prevent a more detailed analysis of its specific actions.

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` `fbb30bebd95cb96c82a492c630d53fbbc0a6d91fcc85540f5500ae7269f98857`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	265155 bytes

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