Office (OOXML) / .XLSX malware analysis — malicious · 9650ceb7c6b2b7d3

MALICIOUS

Office (OOXML) / .XLSX

26.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300

MD5: 2a504b56e65f54b15ac2f6349cdc8fb8 SHA-1: 9f34ed4cd6e672d35c6b6d569f6c1792933bf530 SHA-256: 9650ceb7c6b2b7d3188e4c9fa8e3654edb38fee4aeed4f0e932ffffca5d798f2

182 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Visual Basic T1204.002 Malicious File: User Execution: Malicious File T1105 Ingress Tool Transfer

The sample is an Excel file containing Excel 4.0 macros. These macros utilize WinAPI functions such as URLDownloadToFileA and ShellExecuteA to download a payload from the URL https://littlegreenhands.org/ds/3.gif and execute it. The presence of these functions and the reconstructed URL strongly indicate a downloader or droppper functionality.

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 https://littlegreenhands.org/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `e732fe4d476378e95e0742d5f5b27980e242739ef14fb6e8f421bf762337d640`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	200455 bytes

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