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

Static analysis result for SHA-256 82dfec47ed383bf5…

MALICIOUS

Office (OOXML) / .XLSX

103.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 45b7ec9ced1902075a8ddcc10faacaba SHA-1: b98d68f42be54c88811f14f2a07367fbb45c9bd9 SHA-256: 82dfec47ed383bf5b3ffe59bdb481cf4a9fd69d7c71e4b0971be02495a8313c2
290 Risk Score

Malware Insights

MITRE ATT&CK
T1218.011 Signed Binary Proxy Execution: Rundll32 T1059.005 Command and Scripting Interpreter: Visual Basic T1105 Ingress Tool Transfer

The file contains Excel 4.0 macros that utilize the FORMULA API to call Win32 functions. Specifically, it constructs a command to execute 'rundll32.exe SysWow64\iix.ocx' and uses the 'urlmon' function to download a payload from one of the provided URLs. The macros also appear to be obfuscated by concatenating strings to form the download URLs and function names. This indicates a downloader or initial access stage for a malicious payload.

Heuristics 7

  • Excel 4.0 macro sheet (3 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.
  • 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: FORMULA 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.
  • ClamAV: Win.Malware.Agent-9983617-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.Agent-9983617-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 6 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://lupus.ktcatl.com/wp-content/uCccWJ/
    • http://123breathe.org/error/Drs/
    • https://packersandmoversbangalorecharges.com/cgi-bin/UrI6GM87K5u2y2pOW/
    • https://greenesqualityflooring.com/error/kUO7NnkpMp2cs/
    • http://new.hssus.org/wp-includes/blocks/eKID0QAfLUS/
    • http://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
931aca2f208be70d374ebb6e3b5ce84d62043710cebea4a63abc358f6e3d2cda		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3792 bytes
xlm_sheet_01.xml
1301a9b68f708ecd53476001d2adc675d5907080f1329990cc388355cfbedfbc		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1278 bytes
xlm_sheet_02.xml
103e1830b20c8ca2f2e6d51a3a81673c3dd315f160a9ecbe580bdab4d6238de1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1275 bytes

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