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

Static analysis result for SHA-256 96e022c8a6dd2f59…

MALICIOUS

Office (OOXML) / .XLSM

267.1 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 77aff97d2a700e5759dd1814a03928d3 SHA-1: 5d9cc51be079a4d46e6fe8c96dcc78708f618839 SHA-256: 96e022c8a6dd2f59f54f33f464bb1c51d703f9bf62cd6dbc42c1165c3f79e5b5
250 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File Execution: Malicious File T1059.005 Command and Scripting Interpreter: Visual Basic T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like FOPEN, FWRITE, and EXEC to write content to a file and then execute it. Specifically, the script reconstructs the path 'C:\ProgramData\LukZIfUngPqqO.sct' and uses FOPEN to write data to it, likely a second-stage payload. The use of these functions indicates an intent to download and execute arbitrary code.

Heuristics 6

  • Excel 4.0 macro sheet (1 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: 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.
  • ClamAV: Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0
  • 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
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
8d250b5ee9002f3213850c96aa33f5d51aeb39d4c4b858d1f6a873100e956ab0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 974841 bytes

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