Office (OOXML) / .XLSX malware analysis — malicious · ca6b1385bf173bf6

MALICIOUS

Office (OOXML) / .XLSX

600.6 KB Created: 2021-10-10 18:55:08 UTC Authoring application: Microsoft Excel 12.0000

MD5: 316b74ffcbb8793761a1370cf2de906d SHA-1: fb94580f787ba237400717c52adb416d2576adae SHA-256: ca6b1385bf173bf62aae9e4d7c138bf97cc54387380b4bbf988783b1e07e47b4

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The primary finding is the presence of an Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. While the macro content is truncated and heavily obfuscated, its presence strongly suggests an attempt to execute arbitrary code. This technique is commonly used for initial access or to download and execute further stages of a malicious payload. Without more readable script content, the specific family and detailed actions remain unknown.

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` `4d07f0f85833c427960603811565b9dd37a2553ca13a23febc979880d448f09e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1560075 bytes

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