Office (OOXML) / .XLSX malware analysis — malicious · 3753fcbfe8bb2077

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 90bace5bc1d62304256f248cd279a6a3 SHA-1: 7df2423d88e967b77d1fac5bab9e449389a440cb SHA-256: 3753fcbfe8bb20773856b62f90710ed75c1faad97c0ba74aebdadaf88a31ac32

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

This XLSX file contains multiple Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. The embedded macro content, particularly in xlm_sheet_01.bin, includes the string "URLDownloadToFile", suggesting the macro's purpose is to download and execute a second-stage payload from a remote source. The ClamAV detection further confirms its malicious nature. The specific family is not identifiable from the provided evidence.

Heuristics 3

Excel 4.0 macro sheet (12 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.GreenOffice12210-9918618-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.GreenOffice12210-9918618-0

Extracted artifacts 12

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `b5aba48cdbc925dbf4cf1fd099252f76e1ccde07778d66ad239dd029d3f4e959`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	363 bytes
`xlm_sheet_01.bin` `514ba565434569c0a538370e537b6c9f5c528e1aa38f0e635f27bd199bac7778`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3023 bytes
`xlm_sheet_02.bin` `047efb69be3aabac5e32c5468a16304585fb8200ae4e3ee22b4ad91ad823f54c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	1787 bytes
`xlm_sheet_03.bin` `0f1e1280117d34354f071590ae05ed4b803774dbb89e255f805496835eaedbb3`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin	618 bytes
`xlm_sheet_04.bin` `f93099eafdd1b1c882fd3d99b878ec6f1a02981e1d97ffc55a5317c481c3f9a7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.bin	618 bytes
`xlm_sheet_05.bin` `02c209dd2dc5e6979e99f6e4a3b776670466e8f2322cc37d317ff8ccfc4b675d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.bin	964 bytes
`xlm_sheet_06.bin` `9546b38eaf75fa2c0d2b9c568cc5cba1bb59a95b391668fa432a2be08c195bcf`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet6.bin	650 bytes
`xlm_sheet_07.bin` `62df625d44e0eb5a196e883fba76b1e7243ad8cf79b1303b4b2e74c9f0db97ac`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet7.bin	423 bytes
`xlm_sheet_08.bin` `861f04f1095e7942cb333088a674476c30702f97a737f71c0139aa7a13b90a77`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	754 bytes
`xlm_sheet_09.bin` `8301bc5278f0fa8a1f30b666f2bae149b2af7f7e8725fc411f414d663b46ea68`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	679 bytes
`xlm_sheet_10.bin` `987c911348779e2ffc43c7db23b3310492dcbfccbd081b8f655607c24dbe81e5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	679 bytes
`xlm_sheet_11.bin` `94af29dac79b320dd48dd0c00ef963dea5cdfa0950ab7c96c958da08ff885679`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet8.bin	757 bytes

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