Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 206c71d0a05cb0c1…

MALICIOUS

Office (OOXML) / .XLSX

66.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: c5cc2cac94471dbb62ec6d47677d76a5 SHA-1: 4576ce6ef69dfa9338e804944a27be81b2c79066 SHA-256: 206c71d0a05cb0c144643b86d0f431bbaa8dda3fedf5224e68fa6df43ead95a9
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The macro sheet contains obfuscated commands that appear to construct paths for a startup directory and an executable file, suggesting it is designed to download and execute a second-stage payload. The specific paths constructed are C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Start-up\ and C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Start-up\a.exe.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
82df2dda5059e9e048db05523dcb72e39a9eb0ddcf653dda57fca1ff3be3c123		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 7203 bytes

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