Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 b80b28cac7201b3f…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 77f3a0718ac8dac2d15f43960dfcb555 SHA-1: ede5f66c88e7c8eba7326c234718895456e5605b SHA-256: b80b28cac7201b3f15c606975a6718f6fca17e41c07599b96d4cd9828eed3a72
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros with WinAPI and download strings. These strings, including URLDownloadToFileA, DownloadToFileA, ShellExecuteA, CreateDirectoryA, URLMon, and Kernel32, strongly suggest the macro's intent is to download and execute a second-stage payload from a remote source. The specific macro sheet name 'xl/macrosheets/sheet1.bin' and the embedded artifact 'xlm_sheet_00.bin' further confirm the macro-based nature of the threat.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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