Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 5b01769fd0911e04…

MALICIOUS

Office (OOXML) / .XLSX

128.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: fe5b8cbc20dd0350f65aa7b2b2648fd3 SHA-1: ed12fba00ec20260602ce75ddf62be84c95053a3 SHA-256: 5b01769fd0911e0412b94a2f10b7a12f3f4e515c6172fefb437f7982723bf77a
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file contains multiple Excel 4.0 macro sheets, which are reassembling formulas to download and execute payloads. The heuristics indicate that the macros are designed to download files from the specified URLs, likely to execute a second-stage payload. The presence of these macros and the download URLs strongly suggest a downloader functionality.

Heuristics 3

  • Excel 4.0 macro sheet (13 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.
  • XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD
    An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.
  • ClamAV: Xls.Downloader.GreenOffice01220-9937699-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.GreenOffice01220-9937699-0

Extracted artifacts 13

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
08b2a21dfd49ba82acc3e98fa2548503ea70375384baae9690f9b9f92ee72a12
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 363 bytes
xlm_sheet_01.bin
75486df1e8fdc8dfcfa9347e2efdacc8c653c3f2057c715406ef8db6742ee804
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 632 bytes
xlm_sheet_02.bin
62069c771b71f4e449852a9717d0e3ee529ecca6497ff21cb92f7f53c4d1b43c
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2766 bytes
xlm_sheet_03.bin
ae5e83e6d426668a5db416906d420732f1fdd9591d423b86f2b9f1dcd9fa44ac
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 1619 bytes
xlm_sheet_04.bin
2cd9dbeea24ca020fd0a4017b931dd97c95e7c0ab519355790f0ba447b4a3039
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.bin 573 bytes
xlm_sheet_05.bin
5009dc8e79faedbbf6d81cc8ab84c37fddbbf642b83acb0a4f501b89844ac3ca
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.bin 618 bytes
xlm_sheet_06.bin
cd13478f2e3c7cf4b2507e646c0ceb5fea3e2f93cca4db2727dc940a10700abb
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet6.bin 766 bytes
xlm_sheet_07.bin
d6cbc03e36305aa993ba351dfcc3c9f2613ba6f5108c24fb559e4b12cff76c9e
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet7.bin 472 bytes
xlm_sheet_08.bin
fe33ad0661ee70bb32c1080c3584fa621afd5781d67903179cd30bf602806937
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet8.bin 423 bytes
xlm_sheet_09.bin
ff4e973b54b80c00d226e9c4a283940eb8435e9810d5d202ee1f5db363852b06
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 754 bytes
xlm_sheet_10.bin
6136e300f8261bd0e71a47aed8dd19bafdab22d27cb4eaa966ba836779f08b49
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.bin 679 bytes
xlm_sheet_11.bin
46a26398a13684a16d8ede38746c526be4025503508fe8a89a3748973af9a2d3
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet4.bin 799 bytes
xlm_sheet_12.bin
52cbcb9c330923e6a38883615db2b9d510da997b15c7142598ab08d9f0a99559
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet9.bin 619 bytes