GreenOffice Office (OOXML) / .XLSX malware analysis — malicious · e47c159e2c89ba34

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: a27b4af8036b8f2b39a1324ab51baf20 SHA-1: bfd91d19dd87c9f27488fe65412257cb0feaf971 SHA-256: e47c159e2c89ba345b515bc6f41aba8a22db7b001cf38bdde04af35c8b4933d6

180 Risk Score

Malware Insights

GreenOffice · confidence 95%

MITRE ATT&CK

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

The sample is identified as malicious by ClamAV with the signature Xls.Downloader.GreenOffice01223-9937701-0. Static analysis reveals the presence of multiple Excel 4.0 macro sheets within the XLSX file. These macros are indicative of a downloader, likely intended to fetch and execute a secondary payload. The specific macro sheet names and the ClamAV signature suggest the GreenOffice malware family.

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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