Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 b03b3324dabb86f7…

MALICIOUS

Office (OOXML) / .XLSX

155.1 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: 45aea0cfe4680ddc7362e355bb5125b7 SHA-1: ec62afd090a8a23a8f4aaea62279182768345a91 SHA-256: b03b3324dabb86f74d4a4ca8ffb5620294bcb34686263cfb6f0f24fec24db00b
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an XLSX file containing multiple Excel 4.0 macro sheets. These macros are known to be used for executing arbitrary code, often to download and run further malicious payloads. The heuristics indicate the presence of these macro sheets, and the truncated script content suggests macro execution. Without further deobfuscation or network activity, the exact payload and delivery mechanism remain unknown.

Heuristics 2

  • Excel 4.0 macro sheet (3 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.
  • XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX
    OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
3b0597c6589aef292dd35e3092ac2928cc99618fd1c4351aaacd2838746d0427
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 5827 bytes
xlm_sheet_01.bin
a5d1eb693d80fb32bcf7f6006c9ec30f68b6183d622658990cc5d765d6c87aa3
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1689 bytes
xlm_sheet_02.bin
0f1d71b1495d1b1f75bc1cde39567bcd1b64e6600f51e782cdb9de3a18cc68c5
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 3722 bytes