Office (OOXML) / .XLSX malware analysis — malicious · 54d8230199caabba

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: c65878847972822baec3f03d8667374f SHA-1: 0c08ad2939d926204171fc23cec7286ca4cb735e SHA-256: 54d8230199caabbab5472a7c92343960101223744e0cab53f7029113d144d77f

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel document containing multiple Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. The ClamAV detection of 'Xls.Downloader.GreenOffice01223-9937701-0' suggests a downloader functionality. Although the script content is heavily obfuscated and truncated, the presence of macro sheets strongly implies an attempt to execute malicious code, likely to download and run a further stage. No specific IOCs like URLs or hashes were directly extractable from the provided script excerpts.

Heuristics 3

Excel 4.0 macro sheet (8 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.GreenOffice01223-9937701-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.GreenOffice01223-9937701-0

Extracted artifacts 8

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `233d417b205fa548ee199db8f7dcde5eec5ed25d77f05e8ea9c00ce21c35b939`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2510 bytes
`xlm_sheet_01.bin` `500952c6629948897d18f1986d28785709479e7f8593807356d0fedc7f951272`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	428 bytes
`xlm_sheet_02.bin` `5a15ced69dee870a7d3a5570d88d6d7f09745990f086317a0ee636a9ed4df291`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	428 bytes
`xlm_sheet_03.bin` `4b15edbbba9a65d33fdb500ff8626d9621bac2195ef74d699735b09b21a8028b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	428 bytes
`xlm_sheet_04.bin` `bf2a739fa56c3d15384a1c3110a865e233378e8fc718fbfef40f953b3883318f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	428 bytes
`xlm_sheet_05.bin` `0107b41473071ac5d8b8cb52a31f8c9f5c2d660b8817625277f4f17623947455`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	428 bytes
`xlm_sheet_06.bin` `96bdb6b024c43a4a919a0b7ca20a7186fc8d758fff92d3c7bf74bb2068e7446a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	428 bytes
`xlm_sheet_07.bin` `e561d2de881f21620feda2d77d70861eff058969308a438af3cd54f04c908a83`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	428 bytes

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