Office (OOXML) / .XLSX malware analysis — malicious · fb7277e845a88a3e

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: eabe1a5b8532164600c1ad3d247e8312 SHA-1: 89aab011ec96a1d9e19a677f2c1c95d444cce692 SHA-256: fb7277e845a88a3ea86052f560e8111c8b2c699806c1118136939a7c50d20c84

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros. The macros appear to be constructing a path to execute a file named 'fnsfunSfgRgnKjFsgNd.exe' from the 'C:\ProgramData\fnsfunSfgRgnKjFsgNd\' directory. This suggests the macro's purpose is to download and execute a second-stage payload from a remote source, which is a common technique for malware delivery.

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` `f4c012590ab8c271d00f493201af998b0dbd5054cb17935895d1563745bc3fe9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4282 bytes

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