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

Static analysis result for SHA-256 a8a6f6c2be764f8f…

MALICIOUS

Office (OOXML) / .XLSX

104.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 10773415646458d5326fd9750ea9557d SHA-1: 9b73d6756f435e69c8cbb59c069d3213975ee480 SHA-256: a8a6f6c2be764f8f86a33fc17d021ff4f71c9e338320698f2e9b51c2b5f8f701
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

The sample is an Excel file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize the FORMULA API to call dangerous Win32 functions, specifically to download a payload from multiple URLs. The document body explicitly shows the construction of a command using 'rundll32.exe' to execute code from 'iix.ocx', which is downloaded from the provided URLs. This indicates a clear intent to download and execute a second-stage payload.

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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