Office (OOXML) / .XLSX malware analysis — malicious · c6eedd89491e7292

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 270a6ac9f1231736b39878298a36d1da SHA-1: 140844802b9acd81804cc8b038799c3f2fd3f541 SHA-256: c6eedd89491e7292dc90085bed2451ee504d4a70ec42e432d6a9144d02a8c721

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Execution T1204.002 Malicious File: Malicious File

The sample is an Excel file containing Excel 4.0 macros. Heuristics indicate the presence of WinAPI calls such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, suggesting the macro attempts to download and execute a secondary payload. The specific URLs and executable paths are not fully extracted due to truncation, but the intent to download and run a file is clear.

Heuristics 2

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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	194023 bytes

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