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

Static analysis result for SHA-256 555737271a58f1b5…

MALICIOUS

Office (OOXML) / .XLSM

36.8 KB Created: 2021-03-10 12:17:24 UTC Authoring application: 16.0300
MD5: 03fd6b515355bb513131951edf43ad5e SHA-1: 1eab5eb7e2158d84f80a2c90fbc1c2cf0e188213 SHA-256: 555737271a58f1b566e2d15afb128ae37c8475923ef73d69480d047f40ed098e
208 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. Critical heuristics indicate the use of dangerous XLM formula APIs like 'RETURN' and 'URLDownloadToFile', suggesting the macro is designed to download and execute a second-stage payload. The presence of hidden worksheets further supports the concealment of malicious activity. While specific IOCs for the payload download are not explicitly listed as malicious, the overall behavior points to a downloader.

Heuristics 6

  • 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.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains vbaProject.bin — 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://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://ns.adobe.com/xap/1.0/
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/photoshop/1.0/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://ns.adobe.com/xap/1.0/sType/ResourceEvent#

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
ec40d14ba412e1dbe333c8735ac575efe72716daf96f6c4619edef1c893fa6fd		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2872 bytes
vbaProject_00.bin
ca0671c1b29f26b8835749b93383485e4e16aa74e59ead3c50c780107005fcd6		 vba-project OOXML VBA project: xl/vbaProject.bin 23040 bytes
xlm_sheet_00.xml
1e633e5755f964e146eb49f60f198990f17dc64877cf12597e720e6877ce422e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 919 bytes

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