Office (OOXML) / .XLSX malware analysis — malicious · 56e5ff88c20be6d4

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: ef8568dd0f9720bb8d79983d742e598c SHA-1: 95e60b5ca8f0581d69846d5d84aedef6522ec695 SHA-256: 56e5ff88c20be6d4a8ce5f22c4c09dc6b8a9daa321c4466d5d68d8626f8ef6b3

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is identified as malicious by ClamAV with the signature Xls.Downloader.GreenOffice01223-9937701-0. Heuristics indicate the presence of multiple Excel 4.0 macro sheets, which are often used to download and execute further malicious content. The embedded macro content is heavily obfuscated, but the overall structure suggests a downloader functionality.

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` `e0440aded7ab94dfa712720e673b4e0f174bdefb91d00826c3ff5ea94eb9f2b0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2679 bytes
`xlm_sheet_01.bin` `2380f6fc7152a9d410adfd7ff8185af954ee15a49c71d4a6dcd922f98492aaf1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_02.bin` `fbe1a872d6408b9d07765472ca97b7e10450cbf2bb64e32ae26cee892cef4a50`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes
`xlm_sheet_03.bin` `e8b7c7423e214ccd33c7b5220eaa8108d2ffb1f2f39aae3b3b7045afe3be7e78`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	484 bytes
`xlm_sheet_04.bin` `ced277ef53700f6fcec2f31e5d7089b59998419223599bf4f57b20af56c682e9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	484 bytes
`xlm_sheet_05.bin` `2b7c33b56eae1761f0499d8a41cb4dd1fdc547795e3273427d6352730bf89a67`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	484 bytes
`xlm_sheet_06.bin` `df7e72f81f3f1388096bb9c6178415bfe9d12093a2c4da8ccc3ae92b0fcf9407`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	484 bytes
`xlm_sheet_07.bin` `f156f5267eeb625bee82f34c0ee6625c6115793f6543db431f1b0326845a1f83`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	484 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.