Office (OOXML) / .XLSX malware analysis — malicious · 3cc4948d4d3cac89

MALICIOUS

Office (OOXML) / .XLSX

242.0 KB Created: 2021-04-15 15:04:02 UTC Authoring application: Microsoft Excel 16.0300

MD5: b4a0b38ff2bd7619e42c0f1d1fb0171b SHA-1: c0e61bcc7139bc2342e5a9eb9a2bc056c475624d SHA-256: 3cc4948d4d3cac89a74284ae4dc49d177b834f295e9f767a46dcd73726b7239d

80 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1204.002 Malicious File

The critical heuristic firing for OOXML_XLM_MACROSHEET indicates the presence of Excel 4.0 macros. The embedded macro sheet appears to be obfuscated but contains references to SHA-512, suggesting it is designed to download and execute a second-stage payload. The external relationship heuristic further supports the idea of the document fetching additional content.

Heuristics 2

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.
External relationship medium OOXML_EXTERNAL_REL

External target in xl/pivotCache/_rels/pivotCacheDefinition1.bin.rels: 2.xlsb

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `37259000a6a7747f43ec23f16b1e335a4b450622dbc589cc42e4872f5317aef2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1941 bytes

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