Office (OOXML) / .XLSX malware analysis — malicious · b2146ce57cfa6785

MALICIOUS

Office (OOXML) / .XLSX

163.0 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: a86310371a18d3cdbe1e452145557480 SHA-1: 2b8c6d9943bf07fe8dd2cdcdff187cc0f582aef2 SHA-256: b2146ce57cfa6785eb1c9a405abc48e844c15a5431b85c653f2bda57e03f7449

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The extracted macro content is heavily truncated and obfuscated, making it impossible to determine the exact payload or execution flow. However, the presence of XLM macros strongly suggests an intent to execute arbitrary commands.

Heuristics 1

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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `58eddde43713c92f6cc06ab7645ec2bbe3ad5634d0503408b9c43f3023ab796e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	410553 bytes

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