Office (OOXML) / .XLSX malware analysis — malicious · de8ef5a97246b7b4

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 5b30f2cfe4dc39c3f63ffab97e1f6870 SHA-1: 74d4fc2388687a9445cab7c95f782e6857de2cde SHA-256: de8ef5a97246b7b4ad1775f0b7831d47d64b217775248a670595675de5f09bc1

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Control T1204.002 Malicious File: User Execution

The sample is an Excel file containing Excel 4.0 macros. The macro executes a WMIC command to create and launch a file named 'excel.rtf' from the 'C:\ProgramData\' directory. This indicates a likely attempt to download and execute a second-stage payload. The specific family is not identifiable from the provided evidence.

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` `ecef65a230aaca523f64006507e2c80d4ad4c7561f543b5fea0fabb33be5d9ea`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	151446 bytes

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