Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 91297db5ba8cbde0…

MALICIOUS

Office (OOXML) / .XLSX

90.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: ccdf8cf75b9b23225c93364e26caa1a4 SHA-1: b604db30b9a655f38dc21cadf90324bd7e22ae8e SHA-256: 91297db5ba8cbde03961bc1224f223e832a2d2a7c6ca985d3b6c4e47e531c7dd
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The embedded macro sheet contains strings that appear to construct a path to a file named 'excel.rtf' within the 'C:\ProgramData\' directory. This suggests the macro is intended to download and execute a second-stage payload from a remote source, likely disguised as an RTF document.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
131a2eebf75d79e1718f2fae582e723b7ef5372074846ce98fc3cebfb7a782cf		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 295952 bytes

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