Office (OOXML) / .XLSX malware analysis — malicious · 13f446c26f285272

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 0b6828b06d983112d15533a7bd051523 SHA-1: 62a2c20df81264e05ed47999b80ac25157543399 SHA-256: 13f446c26f28527265dee889d4860175eb87374cf45da8275f752042e9483aac

120 Risk Score

Malware Insights

MITRE ATT&CK

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

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The heuristics indicate the presence of WinAPI strings like URLDownloadToFileA and ShellExecuteA, suggesting the macro attempts to download and execute a second-stage payload. The macro sheet itself is large and contains obfuscated data, further supporting a downloader or dropper role.

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

Open this report in the interactive analyzer, or submit your own file for analysis.