Office (OOXML) / .XLSX malware analysis — malicious · 7e92103a8f4835e6

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: fc3f544b484acabc79a41b323c3e66cc SHA-1: 3e6ba2d820ec8856e6338d3af4d9a64791bb83f1 SHA-256: 7e92103a8f4835e637c9abe9feb5ba468ed5fddd2417a4b2d343f0dcb6357f39

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 file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings indicative of WinAPI calls for downloading and executing files, such as URLDownloadToFileA and ShellExecuteA. A reconstructed URL, http://162.241.115.60/q/1.gif, is present and likely serves as the source for a second-stage payload. The presence of these elements strongly suggests an attack pattern involving macro-based malware delivery.

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 http://162.241.115.60/q/1.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `88bbfd9c46e480ac4f7ac203afcf9ebcf31b2422c88e27a92bef8993e8f14c40`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	194725 bytes

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