Office (OOXML) / .XLSX malware analysis — malicious · 9d2cf649291ff8b4

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 8bc06fc1f83e910defd24edbdafb607b SHA-1: 9db12ca68eee24653c9e7e5de9a757cc1ccaaee6 SHA-256: 9d2cf649291ff8b45ca18f5a29d3fb4ca97126d0d843a8916e9a4eff10298c51

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Control

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The macro script uses 'wmic process call create' to execute 'mshta' with a local file path 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to download and execute a second-stage payload, likely disguised as an RTF document, from the ProgramData directory. The exact nature of the payload within 'excel.rtf' cannot be determined from the provided script excerpt.

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` `674e8d976fb7359ec4eb3c3fa8665940a6a33376743a2c4ee61ba191b440a919`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	161717 bytes

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