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

Static analysis result for SHA-256 c07de69ec2f0ca0c…

MALICIOUS

Office (OOXML) / .XLSX

104.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 2b388ee892da89388c8caf845e164021 SHA-1: 98c91c480d23fec144346146f6321c842e981ea1 SHA-256: c07de69ec2f0ca0cc8703075551643ba9422ecc786aec304829e6f0f7fc777ee
310 Risk Score

Malware Insights

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

This Excel file contains Excel 4.0 macros that leverage dangerous formula APIs to download and execute a payload. The macros construct a command to execute 'rundll32.exe' with arguments pointing to 'iix.ocx' and a URL. The script explicitly reconstructs the URL 'http://thangnhomlocphat.com/lhwn3i_malware/F5V/' for downloading the payload. The presence of multiple suspicious URLs and the use of Excel 4.0 macros for execution strongly indicate a malicious downloader.

Heuristics 8

  • 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-9991551-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.Agent-9991551-0
  • 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.
  • External relationship medium OOXML_EXTERNAL_REL
    External target in xl/externalLinks/_rels/externalLink1.xml.rels: 1.xlsm
  • 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://thangnhomlocphat.com/lhwn3i_malware/F5V/
    • http://b-lubisi-motivational-speaker.com/wp-admin/WRsbnGckV0NGkx8jd/
    • http://mail.skgevents.com/wp-includes/hRMV3zxexKv5RV/
    • https://disruptia.io/licenses/8UFMms/
    • http://sellin.app/wp-admin/isE7aHKfDlS/
    • 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
449e3a4676c371265bdc6fcfea1d283110239a1c89a653258cfab0d7b952ddc3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1277 bytes
xlm_sheet_01.xml
d5af617fba7b23ec0bca520f81892add6fb515970ac26e31d4dbd6a9598ebfde		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1152 bytes
xlm_sheet_02.xml
a355d55add136d7e41aae0f697107093276374784273f7342b99a479761049c4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3546 bytes

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