Office (OOXML) / .XLSX malware analysis — malicious · 85278a1649ffd17d

MALICIOUS

Office (OOXML) / .XLSX

96.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: f1107ae8c76f3ac6c7691fa5a857b206 SHA-1: b69597b25562a96547402d9bcadc096a340b8a69 SHA-256: 85278a1649ffd17dae84fce72827f804b0091b907efd841ac95f6b4644fd8d5a

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The file contains multiple Excel 4.0 macro sheets, indicating a macro-based attack. The scripts explicitly contain URLs such as 'http://Z' and commands to download and execute payloads using 'regsvr32' with filenames like 'C:\ProgramData\Volet1.ocx'. This strongly suggests the file's purpose is to download and run a second-stage malicious component.

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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `df103f6996091bf9081dd2132038b8868481aa010126d923f5a8ff091364cf44`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	363 bytes
`xlm_sheet_01.bin` `7955917fd621131a5ff0fffb6d9e40cabd68e8575f06e760aec721c0b9edd7ef`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1615 bytes
`xlm_sheet_02.bin` `83c39c908241239708ace91ff7a234f390b78c9b9a6ca890149a0af74d5e6258`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	2813 bytes

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