Office (OOXML) / .XLSX malware analysis — malicious · b8e025ac9e705cfb

MALICIOUS

Office (OOXML) / .XLSX

70.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: a115f439f6ca9e8c6cb8877674509472 SHA-1: 607c339a86d02ad53765cf5ad50f29eedf457a2e SHA-256: b8e025ac9e705cfb01ed1fee9fd0f567bca186cbabf4b74760f3d89c3f471ec8

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The embedded macro sheet contains strings that appear to construct a path for a malicious file, likely 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to download and execute a second-stage payload from a remote location, which is a common technique for initial access and malware deployment.

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` `60304cbe14245a054f91773eae1332a5e7340354ece88ccd7c81491664777158`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	107654 bytes

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