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

Static analysis result for SHA-256 1b672299b7d6bfe0…

MALICIOUS

Office (OOXML) / .XLSX

97.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 3d95beb98534d93dab412072c1965335 SHA-1: 0cd14f746eb86b088a23aa85edaac5d5abb5725f SHA-256: 1b672299b7d6bfe0490514ee5a23e26ababf4f6e750ba54f7e8a796809fbc25c
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The sample contains multiple Excel 4.0 macro sheets, identified by critical heuristics. These macros appear to be designed to download payloads from the URLs 'http://Z/Z/Z/C:\ProgramData\Volet1.ocx', 'http://Z/Z/Z/C:\ProgramData\Volet2.ocx', and 'http://Z/Z/Z/C:\ProgramData\Volet3.ocx'. The macros then attempt to execute these downloaded files using 'regsvr32'. The ClamAV detection name 'Xls.Downloader.Docusign112101-9908076-0' further supports its role as a downloader.

Heuristics 3

  • 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.
  • ClamAV: Xls.Downloader.Docusign112101-9908076-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Docusign112101-9908076-0

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
30e7f1eb7b7cda9226667aa44630e34cb4e61815c9b73ffde1c06f2d016d24d9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 363 bytes
xlm_sheet_01.bin
924c95acbe52d08cb50364609116239c27cf91b6440c18d7744972648a370d60		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2900 bytes
xlm_sheet_02.bin
e80c1b37f3c5cec1142f106d8141d8a69bae7bc3fbf9a747d153a562b95978ef		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1676 bytes

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