Office (OOXML) / .XLSX malware analysis — malicious · 61287327b0cb7031

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 584a21889c8fd238d1fe48c651322d59 SHA-1: f1776637096d03065ce8530cc305d42b8b0d4fe0 SHA-256: 61287327b0cb7031ef0ffc2082906f9fa4ce6af74309afb8a98acc8845170d5f

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. These macros contain strings related to WinAPI functions such as URLDownloadToFileA and ShellExecuteA, suggesting the intent to download and execute a secondary payload. The presence of these WinAPI strings and the overall structure points to a downloader or droppper malware.

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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