Office (OOXML) / .XLSM malware analysis — malicious · a3dfa1523b6029b9

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: 8dde09c78579caeb7c420b4dcd2be8da SHA-1: 5fe60d57237548f62e3313d03e5e056184204ed5 SHA-256: a3dfa1523b6029b94ec05e06b7cdfc4af47ebf0e3bbd58cf141a4a5fc31f1724

130 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. These macros utilize dangerous functions like FOPEN, FWRITE, and FCLOSE to construct and write a file to disk. The reconstructed path for this file is C:\ProgramData\ZyiBoBaLqnp.vbs. Additionally, an ALERT function is used to construct the string "Error! Sending report to Microsoft.", likely as a decoy or obfuscation. The use of these functions indicates the sample's intent to download and execute a second-stage payload.

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` `fa77a740c43a9dd81ab17b66ba8ebb67b8703300b7d40298ed5b1dad5230656c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5891 bytes

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