Office (OOXML) / .XLSX malware analysis — malicious · 753b2e4b0e13bfed

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 7a20fac25766e79caf8e8f1a0464ef14 SHA-1: ffb2e1b8d233ab164a7988f03d3de2a39e4c2497 SHA-256: 753b2e4b0e13bfedb57d264f8d94eb1c15dc30f1f9c74d756893be2c283feb6b

120 Risk Score

Malware Insights

MITRE ATT&CK

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

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The heuristics indicate the presence of WinAPI strings related to downloading and executing files, such as URLDownloadToFileA and ShellExecuteA. This suggests the macro is designed to download and run a second-stage payload from a remote source.

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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