Office (OOXML) / .XLSX malware analysis — malicious · f021c2af174404c5

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 693cc31e09b16025baaf65c7ee741f40 SHA-1: 47068bc4ed70348179fc12ae9c79f1366f78a4e2 SHA-256: f021c2af174404c57ddd475708593c0aece1bd78351aecebb49543dfa31c2cc6

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1204.002 Malicious File

The sample is an XLSX file containing multiple Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. One of the macro sheets, xlm_sheet_01.bin, reconstructs the string 'C:\ProgramData\Vdscytujcyk2.ocx', likely a payload filename. Additionally, the macro sheets contain IP addresses such as '158.69.133.79', which are likely used for downloading the payload. The ClamAV detection 'Xls.Downloader.GreenOffice12210-9918618-0' further supports its role as a downloader.

Heuristics 3

Excel 4.0 macro sheet (10 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 10

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `1831135e27aa3fcd07a3f5d821795870a9f5e2355b7df9188a6d0efdf6149bbb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	363 bytes
`xlm_sheet_01.bin` `69436d752fa0382383e5ce52655fe873b5f13f5a6b2c5a1620006a2d20f1a212`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	679 bytes
`xlm_sheet_02.bin` `c9110258eb7599b6539b96953216c37eb03a89b818f06f26e7b5a050df3c8055`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3192 bytes
`xlm_sheet_03.bin` `c5cf69ff326f2193144285337eb631e8b55c5b7d68e9d1afdd6c5a4475f6a8e8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	1744 bytes
`xlm_sheet_04.bin` `6264f7040798e479d8b719b54ebfb6b4bd1291c4ec18419c23cd91cc65e7139a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin	964 bytes
`xlm_sheet_05.bin` `0c3bb474a0790c074482dd875285079db535bcdda740afbfd69f15533c9d5e9e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	679 bytes
`xlm_sheet_06.bin` `510054af1007d9c45cece34f91c43b3667f6bdffa540f8421121e4a31b4d06fd`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.bin	650 bytes
`xlm_sheet_07.bin` `5e5536e6d532eaf651de3541a61f2a781111f06103c51ffc02137dfe2fcc4f73`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.bin	423 bytes
`xlm_sheet_08.bin` `5d56dcd95d8e1a6266c5d40d84c33db51dbe1a8e5e2330a03ed9217f7069e910`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet6.bin	757 bytes
`xlm_sheet_09.bin` `c427f61e6f981c77c7354ad13a6a437981eaaf181a08b9f242806e2298c3e477`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	754 bytes

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