Office (OOXML) / .XLSX malware analysis — malicious · c4373ae06104ee01

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: f84c2c0b7f0a18bcada9b538a31dd212 SHA-1: 57fba857a56d0e7f6a7eca29ea9d3dd5258ff34a SHA-256: c4373ae06104ee011010d5a26f64d58cc1e9cc3b94f21bb425c9d07b19a5da5f

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing an embedded Excel 4.0 macro sheet. This macro executes a 'wmic' command to create a process that runs 'mshta' with a specific file path, 'C:\ProgramData\excel.rtf'. This indicates the macro's intent is to download and execute a second-stage payload from the specified file, likely to achieve further system compromise. The macro itself is heavily obfuscated, but the command execution is clear.

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` `8acb3eeacc1bc222d8d6465453aee2348eb48142805c4c3b2ce561be3a34f8a8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	69837 bytes

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