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

Static analysis result for SHA-256 dd589bbbfcec2265…

MALICIOUS

Office (OOXML) / .XLSM

131.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: db35212aa7fbb90f60c862a82fc4f34c SHA-1: 9167a3c7816d6cba5335c74da2fc2c786b9c131e SHA-256: dd589bbbfcec22650ed4aeb33606b6d9ee4b2afdce6cb2e22435f34348714f81
190 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell T1105 Ingress Tool Transfer T1204.002 Malicious File

The sample is an XLSM file containing Excel 4.0 macros. Heuristics indicate the use of dangerous functions like FOPEN, FWRITE, EXEC, and RETURN, which are commonly used to download and execute payloads. The macro code attempts to construct a file path 'C:\ProgramData\LZbir.rtf' and write to it, suggesting a downloader or dropper functionality. The presence of an Auto_Open defined name further confirms the intent to execute macros upon opening.

Heuristics 5

  • 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, EXEC, 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.
  • 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
c86ac7a3cb293743d9307e2c52dcb0a436b840247f23d9de2b2fce9b23973d2b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 4425 bytes

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