Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 2f1a1876ace64c90…

MALICIOUS

Office (OOXML)

38.0 KB Created: 2020-09-20 21:17:44 UTC Authoring application: Microsoft Excel 16.0300
MD5: f83fd3b81e2017c59108f8b678b0fbfe SHA-1: 15a026231075b59abfb4cfabdbfdfb096575d355 SHA-256: 2f1a1876ace64c903d59ad47f1b99fbd622caa4968b238e69bd1d42b7b9b945c
210 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros, specifically using the EXEC function to download a payload from 'http://iurl.vip/nulvn' to '%Temp%\AmCrA.exe' and then execute it using PowerShell. The macro also includes a command to execute a downloaded file after a delay, indicating a downloader functionality.

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: EXEC 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.
  • Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • Hidden worksheet (veryHidden) 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://iurl.vip/nulvn
    • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
b1f8b8aa89e051bcb8cc51595b6f9225653b0997418492f15f4d045e1426abb8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 1637 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 shell/COM execution token(s).

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