Office (OOXML) / .XLSX malware analysis — malicious · bc96c38e3f85c439

MALICIOUS

Office (OOXML) / .XLSX

33.8 KB Created: 2020-04-29 13:43:05 UTC Authoring application: Microsoft Excel 16.0300

MD5: 31927dbd3bfae76511681911beca4348 SHA-1: 6c6680659b09d18ccab0f933daf5bf1910168b1a SHA-256: bc96c38e3f85c43923a37f57c096eb5b3913b516dbcb11b46cb9cfd0c1d167ce

128 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Execution T1059.001 PowerShell: PowerShell T1204.002 Malicious File: Malicious File

This XLSX file contains multiple Excel 4.0 (XLM) macro sheets, which are rarely used in legitimate documents. The heuristics indicate the use of dangerous XLM functions such as CALL, RUN, FORMULA, and HALT. These functions are typically used to download and execute arbitrary code from external sources, bypassing traditional VBA security measures. The presence of hidden sheets further suggests an attempt to conceal malicious activity.

Heuristics 5

Dangerous XLM formula APIs: RUN, CALL, HALT, FORMULA 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.
Excel 4.0 macro sheet (5 sheet(s)) high 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.
Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 5 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.openxmlformats.org/officeDocument/2006/relationships
- http://schemas.openxmlformats.org/markup-compatibility/2006
- http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
- http://schemas.microsoft.com/office/spreadsheetml/2014/revision
- http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
- http://schemas.microsoft.com/office/spreadsheetml/2016/revision3

Extracted artifacts 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `d286de097658367aefac32ee6fe426b03b50af356f8b56094aaed39be307edbd`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	61161 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 shell/COM execution token(s).
`xlm_sheet_01.xml` `14d183c1ac1270dc4e9d0ce2317894b85c465a49611fcf18e0e3928875b55011`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.xml	37531 bytes
`xlm_sheet_02.xml` `27db94ea837734f57fc5208f2670f0d97dce18db72ad17cc1384cf213fb46ba9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.xml	1086 bytes
`xlm_sheet_03.xml` `56ff7f75a2cbed406c8c3f1b863a1290dd4374f43ce733f76ee7d015ea94d6fd`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.xml	1086 bytes
`xlm_sheet_04.xml` `095b278e16328473a06a8775aa636956de9034e66a07cbe00f446df7a979e773`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.xml	1086 bytes

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