Office (OOXML) / .XLSX malware analysis — malicious · a43e8603987efe13

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 42f4d5fe5d9b206cac7ab7dde9ad52c5 SHA-1: 03b74d04cb10363397c79f18c2389717769ce30b SHA-256: a43e8603987efe135d758a89fc8a45091db336769b68bab1e058807d80effedf

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. These macros are known to be used for executing arbitrary commands. While the specific commands are truncated in the provided evidence, the presence of these macros strongly suggests an intent to download and execute a secondary payload, 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` `bde8aa242237283c45bad6ff242a3df5dc8c4ec346d4eae8044ec463b1b4ed04`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4204 bytes

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