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

Static analysis result for SHA-256 7363f433021cff22…

MALICIOUS

Office (OOXML) / .XLSM

57.8 KB Created: 2021-01-27 09:16:15 UTC Authoring application: 16.0300
MD5: 1815ffa156080703aad8c51069250a4f SHA-1: aa299b06cb3e12bc87d46863b6bfd5cd227fac4b SHA-256: 7363f433021cff220b98f1ea723e2bac724a2241f3225500a530e75cb1eb3025
350 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1566.001 Spearphishing Attachment T1105 Ingress Tool Transfer

The sample is an XLSM file containing VBA macros, including an Auto_Open subroutine. Critical heuristics indicate the use of URLDownloadToFileA for downloading a payload and the presence of Excel 4.0 macros with dangerous functions like RETURN, suggesting a multi-stage attack. The primary function of this file is to act as a downloader for further malicious activity.

Heuristics 9

  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • 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.
  • Dangerous XLM formula APIs: RETURN 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-9827069-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.Agent-9827069-0
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains a VBA project — VBA macros present
  • 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
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
977f2d6cd2e75d8aa4f847fb1a819beb1ae65eef3a2e9a0aeaa895cadd496880		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2779 bytes
vbaProject_00.bin
ce575b8164d74b90498fa9dcd92e6826f68e1b789e863f7a5c895b9d0c6b9361		 vba-project OOXML VBA project: xl/vbaProject.bin 19968 bytes
xlm_sheet_00.xml
80f6f0ca9cead0c0a655de5d7db416bfc33bc1e27df33d7a656bb4f465e941e5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1095 bytes

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