Office (OOXML) / .XLSM malware analysis — malicious · ae7e543fdbcf720d

MALICIOUS

Office (OOXML) / .XLSM

111.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 140f26956439f2543dc1a62cf6c2bb76 SHA-1: 9b59acf74f9099ea449e051cce0570b082ab16a5 SHA-256: ae7e543fdbcf720db3e296cdc5f34d294cc71ac4c6db3fb8a30e85aaece3ffd1

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell

The file is an XLSM document containing Excel 4.0 macros. The macros utilize dangerous functions such as FOPEN, FWRITE, FCLOSE, EXEC, CALL, REGISTER, and FORMULA to download and execute a second-stage payload. Specifically, the FOPEN function is used to create a file at 'C:\ProgramData\AgLK.vbs', and the EXEC function is likely used to run it. The presence of these functions and the hidden worksheet strongly indicate a malicious intent to execute arbitrary code.

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.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `24a29f7ba116aeec9f47e6f029e3b20627130322e6ae13aff92bb88b6c649479`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5105 bytes

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