Office (OOXML) / .XLSX malware analysis — malicious · 4f2e422da958d48b

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 0e70908917edf9f732e282f4326db8a7 SHA-1: 7766b03ddb11b46bba6dd433e530e4d18655dfb9 SHA-256: 4f2e422da958d48bf2ceebcb1109c01a5a35f18f8979ce40a5a303d907c4ccb4

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing an embedded Excel 4.0 macro sheet, as indicated by the OOXML_XLM_MACROSHEET heuristic. The macro executes a 'wmic process call create' command. This command is used to launch 'mshta.exe' with a specific file path, 'C:\ProgramData\excel.rtf', suggesting it's intended to download and execute a second-stage payload. The macro's obfuscated nature and the use of 'mshta' point towards a downloader or droppper functionality.

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` `94ab8fe5363a6dbf9ee790e165d9983e52f4dd3ea3135cee9b07e6aa51417ae2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	107582 bytes

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