Office (OOXML) / .XLSX malware analysis — malicious · d836a4c61aec0934

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 561b4b505cebc6225c75409c2b8bef54 SHA-1: 8782a9c7d7c96371db562cafda9a327e589235c0 SHA-256: d836a4c61aec09343914b4cd215b67fe259acfcfcfac2b0a477ad5d610cdc448

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file 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 name 'Xls.Downloader.GreenOffice01223-9937701-0' strongly suggests that these macros are designed to download and execute a secondary payload. No specific URLs or commands were directly extractable from the truncated script content, but the overall pattern points to a downloader.

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` `0fc8e066703330beb0acb963cc90c864ba9d7a35a9857de7f07543eadd5d8ecf`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	484 bytes
`xlm_sheet_01.bin` `bf6715d9fae02136a7d6693b0ac7c420e37154df417d0c5bc8d8b5a748556dac`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	484 bytes
`xlm_sheet_02.bin` `78c400169fb4fb9a22c987f904afcf0733dcd9b50d30205a6305a30e3e201fd8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2679 bytes
`xlm_sheet_03.bin` `dc492d30ddc2bac398d8b712a2dbbe5e3639e42b759dc41165cdc40f8bbe233d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	484 bytes
`xlm_sheet_04.bin` `b0f3bfa980b44cd091b93eaa2d90fa38b47a49700d4556c470b3563537690d9d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_05.bin` `dec3f15faf62c14843387eba63e2247394d04864293823ccfe6f2e6f8b9e3fd8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes
`xlm_sheet_06.bin` `94f4f9a5c419e00c67505628fb5f2ad897edf8744c6539288147e8eae078975a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	484 bytes
`xlm_sheet_07.bin` `46b4bfc3a91f065aa470b2ea9dbad4342ec52708efca6655feb50bef938cbdaa`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	484 bytes

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