Office (OOXML) / .XLSX malware analysis — malicious · fadbd61772266a8d

MALICIOUS

Office (OOXML) / .XLSX

236.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-09

MD5: afb6627a8c56f0c981250fec9c74cebe SHA-1: aad27786a9900d46ac134ce767b8ccd09708d4aa SHA-256: fadbd61772266a8de153f4f1470f255fab37f34d20715390bcbf90a3b089bbe2

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The sample contains multiple Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. Analysis of the macro sheets reveals functions like 'URLDownloadToFileA' and 'CreateDirectoryA', along with embedded IP addresses that appear to be URLs. This strongly suggests the macro's intent is to download and execute a second-stage payload from these remote locations. The ClamAV detection of 'Xls.Downloader.GreenOffice12210-9918618-0' further supports this conclusion.

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` `62a2f8e4475eb24afcab38028c0d82e78f99db75dbecb4efa523fabd2eaa3a73`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	1019 bytes
`xlm_sheet_01.bin` `bc50ee9dc9f8987ecbf875d1ec4ebc082b22d1bd2ac11d23e66f331ec30fe9d0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	708 bytes
`xlm_sheet_02.bin` `70a043b6d32cb7cfdcfa6cee922a59ab2e02452da3d1d5eb995db292d1a1fe20`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	2234 bytes
`xlm_sheet_03.bin` `a71ea1757d50ddd1bc4c5bec099f6bf47fe18bd0d69062c6677f86f48b201c10`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	1465 bytes
`xlm_sheet_04.bin` `e9ae29a96ab5f1958f0bca02b1fbf3cc7c67024b5a92a9896c0f2babe0f5fed4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin	785 bytes
`xlm_sheet_05.bin` `e6e2a27dbd256b7c73eb99a4c2372dd82501ce61095f95570441e02bc16e677e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	708 bytes
`xlm_sheet_06.bin` `d8b03cf464cad8dbf716b035891dad4260cc9e346db3a0ef8ba99e8758ea7df7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.bin	785 bytes
`xlm_sheet_07.bin` `df925c905f3c2d349884c2ae9aeec466a703b6f4aa0e828f8dd0629d3ca3f53d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.bin	622 bytes
`xlm_sheet_08.bin` `a43047011ff92284d88f558745569fe5ec75a12bddcd817d1ad59f207e92e41a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet8.bin	423 bytes
`xlm_sheet_09.bin` `1277af80096b4ab6d12bc1eee10392d1db758c49ca057d2d4dd9c93f47113bff`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet6.bin	472 bytes
`xlm_sheet_10.bin` `c0b962039cdc82ce8ead7751e55933182c5e61169851312ff76b9003e7dbad8f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	783 bytes
`xlm_sheet_11.bin` `2013fce74caf8c9665340395064c6d0a68ff76b60474fe265082cadf7c65dd49`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet7.bin	423 bytes

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