Office (OOXML) / .XLSX malware analysis — malicious · 0db75c326af6e7e9

MALICIOUS

Office (OOXML) / .XLSX

315.1 KB Created: 2020-05-11 14:19:29 UTC Authoring application: Microsoft Excel 15.0300

MD5: 28ab25f8f1addbd3c9a93d156e7407b1 SHA-1: e5280201f915b7f707dab1084eee9c548a93e6ed SHA-256: 0db75c326af6e7e9202ec260ea5c61c91dcaf79190896edde67e2dc83bdc5e42

182 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1105 Ingress Tool Transfer T1204.002 Malicious File

This Excel file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros reconstruct a URL and use WinAPI functions like URLDownloadToFileA to download a second-stage payload, likely an executable, from 'http://marspetcarelawsuit.com/xls.png'. The downloaded file is then likely executed using ShellExecuteA.

Heuristics 4

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.
Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS

Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
URL reconstructed from XLM cell array (1 URL) critical OOXML_XLM_CELL_ARRAY_URL

Excel 4.0 macro sheet stages its payload URL across individual numeric cells (one ASCII charcode per cell) or inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation. The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF12 record stream of every worksheet and macrosheet part and decoding RK/inline-string cells in both row-major and column-major order.
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.

URL http://marspetcarelawsuit.com/xls.png

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `ba11d3dad4be7a2215f9ee66438023a1a62d456afd4b5aa8ee74f10c54b581e1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	54095 bytes

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