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

Static analysis result for SHA-256 d6a5d4bec8bc8821…

MALICIOUS

Office (OOXML) / .XLSM

123.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 515c3151e59823e47555c54efcb79f29 SHA-1: d15fba9c73d97dc6e117222aa054efbe841bab9b SHA-256: d6a5d4bec8bc88217fea61b21c8b346d80fcbee3dcf602d717f8197cb44ca840
130 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. The macros utilize dangerous functions like FOPEN, FWRITE, FCLOSE, and EXEC to download and execute a second-stage payload. Specifically, the macro attempts to create a file named 'MWwsPw.vbs' in the 'C:\ProgramData\' directory and then execute it. The ALERT function is used to display a deceptive message to the user, likely to mask the malicious activity.

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.
  • Dangerous XLM formula APIs: FOPEN, FWRITE, FCLOSE, 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
75e595069b33675711cf9672a5c32eb05e6611ac6c09e2e547127b8848bf25df		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5537 bytes

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