Office (OOXML) / .XLSX malware analysis — malicious · 6d6ff6f138defb2b

MALICIOUS

Office (OOXML) / .XLSX

269.3 KB Created: 2021-04-15 14:49:02 UTC Authoring application: Microsoft Excel 16.0300

MD5: e86b9229ec1b692dff17c074843d27da SHA-1: 61598ee67b6f4f5ac01a5f0752dfe3324d00c66f SHA-256: 6d6ff6f138defb2bb7602c08c1cb22930f5e30ef264eeaf760f99d4ca95beca7

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros are designed to reassemble a payload that uses certutil to decode and execute a file. This indicates a downloader or dropper functionality.

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.
XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD

An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `a523e58dedcf11f1e5120f42d2a6ee960ad2dbbfa8d1289e9b296f681779bf90`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1945 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.