Office (OOXML) / .XLSX malware analysis — malicious · 1e3a3a4bf1083910

MALICIOUS

Office (OOXML) / .XLSX

94.2 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300

MD5: f41d0cb710640b01e64c5c0cd57d439d SHA-1: 32923f0501bc37f7e053756ef1036e385f7b65d9 SHA-256: 1e3a3a4bf1083910fdca5163c41f94e2fe74ef1c7ba016a45c7f0452f6017352

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The file is an XLSX document containing embedded Excel 4.0 macro sheets, identified by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. These macro sheets are designed to execute arbitrary commands upon opening. While the exact commands are truncated and obfuscated, the presence of such macro sheets strongly suggests an intent to download and execute a secondary payload. No specific family could be identified due to the obfuscation and lack of clear indicators.

Heuristics 2

Excel 4.0 macro sheet (2 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.
XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX

OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `3f8db13af710fc4012ee5afb18ac21606b10f6307f1ca1192d9c191e0487c25b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	9034 bytes
`xlm_sheet_01.bin` `f697ee5ed6aa2dc2333e560eda58b21fd0a9b4315f1cc12bcc32630116f57256`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	1176 bytes

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