Office (OOXML) / .XLSX malware analysis — malicious · a02ea9c8255c0992

MALICIOUS

Office (OOXML) / .XLSX

113.6 KB Created: 2021-03-05 04:08:28 UTC Authoring application: Microsoft Excel 16.0300

MD5: bf7c56e80af8e2ba7bd09fe4b0c9c633 SHA-1: c62bb6c2fd2f85f4a4720ca5aa7af2eb7849bc7f SHA-256: a02ea9c8255c0992cb9f021fbfca4cbcdec165658a5542d89151ce369cda30c0

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The ClamAV detection further confirms its malicious nature as a downloader. The embedded macro sheet is heavily truncated, preventing a detailed analysis of its specific actions or any reconstructed IOCs. However, the presence of Excel 4.0 macros strongly suggests an attempt to download and execute a secondary payload.

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.
ClamAV: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Doc.Downloader.Trojan-bf70f023603538ee-bf70f023603538ee-9950269-0

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `9640861874c6c7f9de3f0e7eb310c8f344c1b287412563d0bcd26d5f086fce7c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	10168 bytes

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