Office (OOXML) / .XLSX malware analysis — malicious · 53f3655f8ffe5948

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 6940de6ca8fbf01ff29889e4fa6cdffd SHA-1: d2771e97b2880d48009fb45ae592587f49268536 SHA-256: 53f3655f8ffe59482ccb7b5bb2a54555c7ee6dda4407146bfb81e9e6a12dadcf

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. The macro appears to be constructing a path to a file named 'excel.rtf' within the 'C:\ProgramData\' directory, likely intended for staging a downloaded payload. The macro is heavily obfuscated and truncated, preventing a full analysis of its execution flow, but the intent is to download and execute a second-stage payload.

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` `57c3bc58f9f066bdc45c791cc495c5ae9c90f5fce4505f619cd2725b90e38d88`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	149343 bytes

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