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

Static analysis result for SHA-256 e940624b71644695…

MALICIOUS

Office (OOXML) / .XLSM

105.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 1e99f26dd626ebf1706b9d772ac8f750 SHA-1: c26fb512eb58f6add7cf86cc6847e2a97c0c5271 SHA-256: e940624b71644695cdfde151381d6ef0682a012dd52f433d4f247a1eb208463f
180 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File T1059.005 Visual Basic T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The presence of an Auto_Open defined name and the use of dangerous XLM functions like CALL and EXEC (as flagged by OOXML_XLM_DANGEROUS_FN) strongly suggest an attempt to execute arbitrary code. The document body contains obfuscated strings that appear to resolve to URLs, likely for downloading a second-stage payload. The specific functions used (CALL, EXEC) are commonly employed to achieve this.

Heuristics 4

  • 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: CALL, EXEC, FORMULA.FILL, 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.
  • 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
    • 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
1ac8164566eb69dad25e2fb55eafdc9b2a3eac004a1f0cc291930400a77c99df		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 230169 bytes

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